diff --git a/CHANGES.md b/CHANGES.md
index 249cbb33..d21b755a 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,5 +1,13 @@
 # SVG-Edit CHANGES
 
+## ?
+
+- Enhancement: Return a Promise for Editor's `setCustomHandlers`,
+    `loadFromString`, `loadFromDataURI` so known when ready and set
+- Docs (Refactoring): Formally specify `Promise` resolve type;
+    add `typedef` for dialog result object; add an
+    `ArbitraryCallbackResult` type
+
 ## 4.3.0
 
 - Fix: Droplets for gradient pickers can now be double-clicked in
diff --git a/editor/dbox.js b/editor/dbox.js
index f02196f3..113353ab 100644
--- a/editor/dbox.js
+++ b/editor/dbox.js
@@ -23,13 +23,19 @@ export default function jQueryPluginDBox ($, strings = {ok: 'Ok', cancel: 'Cance
     btnHolder = $('#dialog_buttons'),
     dialogContent = $('#dialog_content');
 
+  /**
+  * @typedef {PlainObject} module:jQueryPluginDBox.PromiseResultObject
+  * @property {string|true} response
+  * @property {boolean} checked
+  */
+
   /**
   * Resolves to `false` (if cancelled), for prompts and selects
   * without checkboxes, it resolves to the value of the form control. For other
   * types without checkboxes, it resolves to `true`. For checkboxes, it resolves
   * to an object with the `response` key containing the same value as the previous
   * mentioned (string or `true`) and a `checked` (boolean) property.
-  * @typedef {Promise} module:jQueryPluginDBox.PromiseResult
+  * @typedef {Promise<boolean|string|module:jQueryPluginDBox.PromiseResultObject>} module:jQueryPluginDBox.PromiseResult
   */
   /**
   * @typedef {PlainObject} module:jQueryPluginDBox.SelectOption
diff --git a/editor/extensions/ext-markers.js b/editor/extensions/ext-markers.js
index 9ab5403d..dea646af 100644
--- a/editor/extensions/ext-markers.js
+++ b/editor/extensions/ext-markers.js
@@ -388,7 +388,7 @@ export default {
 
     /**
     * @param {"start"|"mid"|"end"} pos
-    * @returns {Promise} Resolves to `undefined`
+    * @returns {Promise<void>} Resolves to `undefined`
     */
     async function showTextPrompt (pos) {
       let def = $('#' + pos + '_marker').val();
@@ -426,7 +426,7 @@ export default {
     // callback function for a toolbar button click
     /**
     * @param {Event} ev
-    * @returns {Promise} Resolves to `undefined`
+    * @returns {Promise<void>} Resolves to `undefined`
     */
     async function setArrowFromButton (ev) {
       const parts = this.id.split('_');
diff --git a/editor/extensions/ext-placemark.js b/editor/extensions/ext-placemark.js
index e904f898..100cbd3f 100644
--- a/editor/extensions/ext-placemark.js
+++ b/editor/extensions/ext-placemark.js
@@ -240,7 +240,7 @@ export default {
     }
     /**
     * @param {Event} ev
-    * @returns {Promise} Resolves to `undefined`
+    * @returns {Promise<void>} Resolves to `undefined`
     */
     function setArrowFromButton (ev) {
       const parts = this.id.split('_');
diff --git a/editor/external/dynamic-import-polyfill/importModule.js b/editor/external/dynamic-import-polyfill/importModule.js
index 13090762..328263fc 100644
--- a/editor/external/dynamic-import-polyfill/importModule.js
+++ b/editor/external/dynamic-import-polyfill/importModule.js
@@ -40,7 +40,7 @@ function addScriptAtts (script, atts) {
 * @function module:importModule.importSetGlobalDefault
 * @param {string|string[]} url
 * @param {module:importModule.ImportConfig} config
-* @returns {Promise} The value to which it resolves depends on the export of the targeted module.
+* @returns {Promise<*>} The value to which it resolves depends on the export of the targeted module.
 */
 export function importSetGlobalDefault (url, config) {
   return importSetGlobal(url, {...config, returnDefault: true});
@@ -49,7 +49,7 @@ export function importSetGlobalDefault (url, config) {
 * @function module:importModule.importSetGlobal
 * @param {string|string[]} url
 * @param {module:importModule.ImportConfig} config
-* @returns {Promise} The promise resolves to either an `ArbitraryModule` or
+* @returns {Promise<ArbitraryModule>} The promise resolves to either an `ArbitraryModule` or
 *   any other value depends on the export of the targeted module.
 */
 export async function importSetGlobal (url, {global: glob, returnDefault}) {
@@ -68,7 +68,7 @@ export async function importSetGlobal (url, {global: glob, returnDefault}) {
  * @author Brett Zamir (other items are from `dynamic-import-polyfill`)
  * @param {string|string[]} url
  * @param {PlainObject} [atts={}]
- * @returns {Promise} Resolves to `undefined` or rejects with an `Error` upon a
+ * @returns {Promise<void|Error>} Resolves to `undefined` or rejects with an `Error` upon a
  *   script loading error
  */
 export function importScript (url, atts = {}) {
@@ -112,14 +112,14 @@ export function importScript (url, atts = {}) {
 }
 
 /**
- *
- * @param {string|string[]} url
- * @param {PlainObject} [atts={}]
- * @param {PlainObject} opts
- * @param {boolean} [opts.returnDefault=false} = {}]
- * @returns {Promise} Resolves to value of loading module or rejects with
- *   `Error` upon a script loading error.
- */
+*
+* @param {string|string[]} url
+* @param {PlainObject} [atts={}]
+* @param {PlainObject} opts
+* @param {boolean} [opts.returnDefault=false} = {}]
+* @returns {Promise<*>} Resolves to value of loading module or rejects with
+*   `Error` upon a script loading error.
+*/
 export function importModule (url, atts = {}, {returnDefault = false} = {}) {
   if (Array.isArray(url)) {
     return Promise.all(url.map((u) => {
diff --git a/editor/locale/locale.js b/editor/locale/locale.js
index ffeece9f..628fea69 100644
--- a/editor/locale/locale.js
+++ b/editor/locale/locale.js
@@ -127,7 +127,7 @@ export const init = (editor) => {
 * @function module:locale.readLang
 * @param {module:locale.LocaleStrings} langData See {@tutorial LocaleDocs}
 * @fires module:svgcanvas.SvgCanvas#event:ext-addLangData
-* @returns {Promise} Resolves to [`LangAndData`]{@link module:locale.LangAndData}
+* @returns {Promise<module:locale.LangAndData>} Resolves to [`LangAndData`]{@link module:locale.LangAndData}
 */
 export const readLang = async function (langData) {
   const more = await editor_.addLangData(langParam);
@@ -366,7 +366,7 @@ export const readLang = async function (langData) {
  * @fires module:svgcanvas.SvgCanvas#event:ext-addLangData
  * @fires module:svgcanvas.SvgCanvas#event:ext-langReady
  * @fires module:svgcanvas.SvgCanvas#event:ext-langChanged
- * @returns {Promise} Resolves to result of {@link module:locale.readLang}
+ * @returns {Promise<module:locale.LangAndData>} Resolves to result of {@link module:locale.readLang}
 */
 export const putLocale = async function (givenParam, goodLangs, conf) {
   if (givenParam) {
diff --git a/editor/svg-editor.js b/editor/svg-editor.js
index 6ff3334a..935133da 100644
--- a/editor/svg-editor.js
+++ b/editor/svg-editor.js
@@ -318,7 +318,7 @@ let svgCanvas, urldata,
  * @param {PlainObject} [opts={}]
  * @param {boolean} [opts.noAlert]
  * @throws {Error} Upon failure to load SVG
- * @returns {Promise} Resolves to undefined upon success (or if `noAlert` is
+ * @returns {Promise<void>} Resolves to undefined upon success (or if `noAlert` is
  *   falsey, though only until after the `alert` is closed); rejects if SVG
  *   loading fails and `noAlert` is truthy.
  */
@@ -348,13 +348,13 @@ function getImportLocale ({defaultLang, defaultName}) {
    * @param {PlainObject} localeInfo
    * @param {string} [localeInfo.name] Defaults to `defaultName` of {@link module:SVGEditor~getImportLocale}
    * @param {string} [localeInfo.lang=defaultLang] Defaults to `defaultLang` of {@link module:SVGEditor~getImportLocale}
-   * @returns {Promise} Resolves to {@link module:locale.LocaleStrings}
+   * @returns {Promise<module:locale.LocaleStrings>} Resolves to {@link module:locale.LocaleStrings}
    */
   return async function importLocaleDefaulting ({name = defaultName, lang = defaultLang} = {}) {
     /**
      *
      * @param {string} language
-     * @returns {Promise} Resolves to {@link module:locale.LocaleStrings}
+     * @returns {Promise<module:locale.LocaleStrings>} Resolves to {@link module:locale.LocaleStrings}
      */
     function importLocale (language) {
       const url = `${curConfig.extPath}ext-locale/${name}/${language}.js`;
@@ -607,10 +607,10 @@ editor.setConfig = function (opts, cfgCfg) {
 * Allows one to override default SVGEdit `open`, `save`, and
 * `export` editor behaviors.
 * @param {module:SVGEditor.CustomHandler} opts Extension mechanisms may call `setCustomHandlers` with three functions: `opts.open`, `opts.save`, and `opts.exportImage`
-* @returns {undefined}
+* @returns {Promise<void>}
 */
 editor.setCustomHandlers = function (opts) {
-  editor.ready(function () {
+  return editor.ready(function () {
     if (opts.open) {
       $('#tool_open > input[type="file"]').remove();
       $('#tool_open').show();
@@ -798,7 +798,7 @@ editor.init = function () {
    * @fires module:svgcanvas.SvgCanvas#event:ext-langReady
    * @fires module:svgcanvas.SvgCanvas#event:ext-langChanged
    * @fires module:svgcanvas.SvgCanvas#event:extensions_added
-   * @returns {Promise} Resolves to result of {@link module:locale.readLang}
+   * @returns {Promise<module:locale.LangAndData>} Resolves to result of {@link module:locale.readLang}
    */
   const extAndLocaleFunc = async function () {
     // const lang = ('lang' in curPrefs) ? curPrefs.lang : null;
@@ -1884,7 +1884,7 @@ editor.init = function () {
   /**
    * @param {PlainObject} [opts={}]
    * @param {boolean} [opts.cancelDeletes=false}]
-   * @returns {Promise} Resolves to `undefined`
+   * @returns {Promise<void>} Resolves to `undefined`
    */
   async function promptImgURL ({cancelDeletes = false} = {}) {
     let curhref = svgCanvas.getHref(selectedElement);
@@ -3041,7 +3041,7 @@ editor.init = function () {
    * @param {external:Window} win
    * @param {module:svgcanvas.SvgCanvas#event:extension_added} ext
    * @listens module:svgcanvas.SvgCanvas#event:extension_added
-   * @returns {Promise|undefined} Resolves to `undefined`
+   * @returns {Promise<void>|undefined} Resolves to `undefined`
    */
   const extAdded = async function (win, ext) {
     if (!ext) {
@@ -4324,7 +4324,7 @@ editor.init = function () {
 
   /**
   *
-  * @returns {Promise} Resolves to `undefined`
+  * @returns {Promise<void>} Resolves to `undefined`
   */
   const makeHyperlink = async function () {
     if (!Utils.isNullish(selectedElement) || multiselected) {
@@ -4432,7 +4432,7 @@ editor.init = function () {
 
   /**
    * @fires module:svgcanvas.SvgCanvas#event:ext-onNewDocument
-   * @returns {Promise} Resolves to `undefined`
+   * @returns {Promise<void>} Resolves to `undefined`
    */
   const clickClear = async function () {
     const [x, y] = curConfig.dimensions;
@@ -4487,7 +4487,7 @@ editor.init = function () {
   let loadingURL;
   /**
   *
-  * @returns {Promise} Resolves to `undefined`
+  * @returns {Promise<void>} Resolves to `undefined`
   */
   const clickExport = async function () {
     const imgType = await $.select('Select an image type for export: ', [
@@ -4724,7 +4724,7 @@ editor.init = function () {
 
   /**
   *
-  * @returns {Promise} Resolves to `undefined`
+  * @returns {Promise<void>} Resolves to `undefined`
   */
   const saveSourceEditor = async function () {
     if (!editingsource) { return; }
@@ -4853,7 +4853,7 @@ editor.init = function () {
 
   /**
   *
-  * @returns {Promise} Resolves to `undefined`
+  * @returns {Promise<void>} Resolves to `undefined`
   */
   const cancelOverlays = async function () {
     $('#dialog_box').hide();
@@ -6045,7 +6045,7 @@ editor.init = function () {
   };
 
   /**
-  * @returns {Promise} Resolves to boolean indicating `true` if there were no changes
+  * @returns {Promise<boolean>} Resolves to boolean indicating `true` if there were no changes
   *  and `false` after the user confirms.
   */
   editor.openPrep = function () {
@@ -6213,7 +6213,7 @@ editor.init = function () {
   * @param {module:locale.LocaleStrings} allStrings See {@tutorial LocaleDocs}
   * @fires module:svgcanvas.SvgCanvas#event:ext-langReady
   * @fires module:svgcanvas.SvgCanvas#event:ext-langChanged
-  * @returns {Promise} A Promise which resolves to `undefined`
+  * @returns {Promise<void>} A Promise which resolves to `undefined`
   */
   const setLang = editor.setLang = async function (lang, allStrings) {
     editor.langChanged = true;
@@ -6336,14 +6336,14 @@ editor.init = function () {
 
 /**
 * @callback module:SVGEditor.ReadyCallback
-* @returns {Promise|undefined}
+* @returns {Promise<void>|undefined}
 */
 /**
 * Queues a callback to be invoked when the editor is ready (or
 *   to be invoked immediately if it is already ready--i.e.,
 *   if `runCallbacks` has been run).
 * @param {module:SVGEditor.ReadyCallback} cb Callback to be queued to invoke
-* @returns {Promise} Resolves when all callbacks, including the supplied have resolved
+* @returns {Promise<ArbitraryCallbackResult>} Resolves when all callbacks, including the supplied have resolved
 */
 editor.ready = function (cb) { // eslint-disable-line promise/prefer-await-to-callbacks
   return new Promise((resolve, reject) => { // eslint-disable-line promise/avoid-new
@@ -6357,7 +6357,7 @@ editor.ready = function (cb) { // eslint-disable-line promise/prefer-await-to-ca
 
 /**
 * Invokes the callbacks previous set by `svgEditor.ready`
-* @returns {Promise} Resolves to `undefined` if all callbacks succeeded and rejects otherwise
+* @returns {Promise<void>} Resolves to `undefined` if all callbacks succeeded and rejects otherwise
 */
 editor.runCallbacks = async function () {
   try {
@@ -6380,10 +6380,10 @@ editor.runCallbacks = async function () {
 * @param {string} str The SVG string to load
 * @param {PlainObject} [opts={}]
 * @param {boolean} [opts.noAlert=false] Option to avoid alert to user and instead get rejected promise
-* @returns {Promise}
+* @returns {Promise<void>}
 */
 editor.loadFromString = function (str, {noAlert} = {}) {
-  editor.ready(async function () {
+  return editor.ready(async function () {
     try {
       await loadSvgString(str, {noAlert});
     } catch (err) {
@@ -6416,7 +6416,7 @@ editor.disableUI = function (featList) {
 * @param {PlainObject} [opts={}] May contain properties: `cache`, `callback`
 * @param {boolean} [opts.cache]
 * @param {boolean} [opts.noAlert]
-* @returns {Promise} Resolves to `undefined` or rejects upon bad loading of
+* @returns {Promise<void>} Resolves to `undefined` or rejects upon bad loading of
 *   the SVG (or upon failure to parse the loaded string) when `noAlert` is
 *   enabled
 */
@@ -6457,10 +6457,10 @@ editor.loadFromURL = function (url, {cache, noAlert} = {}) {
 * @param {string} str The Data URI to base64-decode (if relevant) and load
 * @param {PlainObject} [opts={}]
 * @param {boolean} [opts.noAlert]
-* @returns {Promise} Resolves to `undefined` and rejects if loading SVG string fails and `noAlert` is enabled
+* @returns {Promise<void>} Resolves to `undefined` and rejects if loading SVG string fails and `noAlert` is enabled
 */
 editor.loadFromDataURI = function (str, {noAlert} = {}) {
-  editor.ready(function () {
+  return editor.ready(function () {
     let base64 = false;
     let pre = str.match(/^data:image\/svg\+xml;base64,/);
     if (pre) {
@@ -6481,7 +6481,7 @@ editor.loadFromDataURI = function (str, {noAlert} = {}) {
  * @param {module:svgcanvas.ExtensionInitCallback} init Config to be invoked on this module
  * @param {module:svgcanvas.ExtensionInitArgs} initArgs
  * @throws {Error} If called too early
- * @returns {Promise} Resolves to `undefined`
+ * @returns {Promise<void>} Resolves to `undefined`
 */
 editor.addExtension = function (name, init, initArgs) {
   // Note that we don't want this on editor.ready since some extensions
diff --git a/editor/svgcanvas.js b/editor/svgcanvas.js
index 0b459a9e..c3a92d8c 100644
--- a/editor/svgcanvas.js
+++ b/editor/svgcanvas.js
@@ -1113,7 +1113,7 @@ const runExtensions = this.runExtensions = function (action, vars, returnArray,
 /**
  * @function module:svgcanvas.ExtensionInitResponse#addLangData
  * @param {module:svgcanvas.SvgCanvas#event:ext-addLangData} arg
- * @returns {Promise} Resolves to {@link module:locale.ExtensionLocaleData}
+ * @returns {Promise<module:locale.ExtensionLocaleData>} Resolves to {@link module:locale.ExtensionLocaleData}
 */
 /**
  * @function module:svgcanvas.ExtensionInitResponse#onNewDocument
@@ -1136,7 +1136,7 @@ const runExtensions = this.runExtensions = function (action, vars, returnArray,
 * @callback module:svgcanvas.ExtensionInitCallback
 * @this module:SVGEditor
 * @param {module:svgcanvas.ExtensionArgumentObject} arg
-* @returns {Promise} Resolves to [ExtensionInitResponse]{@link module:svgcanvas.ExtensionInitResponse} or `undefined`
+* @returns {Promise<module:svgcanvas.ExtensionInitResponse|void>} Resolves to [ExtensionInitResponse]{@link module:svgcanvas.ExtensionInitResponse} or `undefined`
 */
 /**
 * @typedef {PlainObject} module:svgcanvas.ExtensionInitArgs
@@ -1152,7 +1152,7 @@ const runExtensions = this.runExtensions = function (action, vars, returnArray,
 * @fires module:svgcanvas.SvgCanvas#event:extension_added
 * @throws {TypeError|Error} `TypeError` if `extInitFunc` is not a function, `Error`
 *   if extension of supplied name already exists
-* @returns {Promise} Resolves to `undefined`
+* @returns {Promise<void>} Resolves to `undefined`
 */
 this.addExtension = async function (name, extInitFunc, {$: jq, importLocale}) {
   if (typeof extInitFunc !== 'function') {
@@ -1416,7 +1416,7 @@ canvas.call = call;
 /**
  * The promise return, if present, resolves to `undefined`
  *  (`extension_added`, `exported`, `saved`)
- * @typedef {Promise|undefined} module:svgcanvas.EventHandlerReturn
+ * @typedef {Promise<void>|void} module:svgcanvas.EventHandlerReturn
 */
 
 /**
@@ -3827,7 +3827,7 @@ this.svgToString = function (elem, indent) {
 * Converts a given image file to a data URL when possible, then runs a given callback.
 * @function module:svgcanvas.SvgCanvas#embedImage
 * @param {string} src - The path/URL of the image
-* @returns {Promise} Resolves to Data URL (string|false)
+* @returns {Promise<string|false>} Resolves to a Data URL (string|false)
 */
 this.embedImage = function (src) {
   // Todo: Remove this Promise in favor of making an async/await `Image.load` utility
@@ -3967,7 +3967,7 @@ let canvg;
 * @param {boolean} [opts.avoidEvent]
 * @fires module:svgcanvas.SvgCanvas#event:exported
 * @todo Confirm/fix ICO type
-* @returns {Promise} Resolves to {@link module:svgcanvas.ImageExportedResults}
+* @returns {Promise<module:svgcanvas.ImageExportedResults>} Resolves to {@link module:svgcanvas.ImageExportedResults}
 */
 this.rasterExport = async function (imgType, quality, exportWindowName, opts = {}) {
   const type = imgType === 'ICO' ? 'BMP' : (imgType || 'PNG');
@@ -4053,7 +4053,7 @@ this.rasterExport = async function (imgType, quality, exportWindowName, opts = {
 * @param {string} [exportWindowName] Will also be used for the download file name here
 * @param {external:jsPDF.OutputType} [outputType="dataurlstring"]
 * @fires module:svgcanvas.SvgCanvas#event:exportedPDF
-* @returns {Promise} Resolves to {@link module:svgcanvas.PDFExportedResults}
+* @returns {Promise<module:svgcanvas.PDFExportedResults>} Resolves to {@link module:svgcanvas.PDFExportedResults}
 */
 this.exportPDF = async function (
   exportWindowName,
diff --git a/editor/typedefs.js b/editor/typedefs.js
index 7422b42e..581654ba 100644
--- a/editor/typedefs.js
+++ b/editor/typedefs.js
@@ -10,10 +10,16 @@
 * @typedef {null|boolean|Float|string|GenericArray|PlainObject} JSON
 */
 
+/**
+* This should only be used when the return result from a callback
+*  is not known as to type.
+* @typedef {*} ArbitraryCallbackResult
+*/
+
 /**
 * @callback GenericCallback
 * @param {...*} args Signature dependent on the function
-* @returns {*} Return dependent on the function
+* @returns {ArbitraryCallbackResult} Return dependent on the function
 */
 
 /**
diff --git a/jsdoc-check-overly-generic-types.js b/jsdoc-check-overly-generic-types.js
index e63367cb..27b4aa8b 100644
--- a/jsdoc-check-overly-generic-types.js
+++ b/jsdoc-check-overly-generic-types.js
@@ -76,16 +76,24 @@ function reduceFalseMatches (file, res) {
       ].includes(line);
     });
     break;
+  case 'editor/external/dynamic-import-polyfill/importModule.js':
+    res.line = res.line.filter((line) => {
+      return ![
+        '* @returns {Promise<*>} The value to which it resolves depends on the export of the targeted module.',
+        '* @returns {Promise<*>} Resolves to value of loading module or rejects with'
+      ].includes(line);
+    });
+    break;
   case 'editor/typedefs.js':
     res.line = res.line.filter((line) => {
       return ![
         '* @typedef {number} Float',
+        '* @typedef {*} ArbitraryCallbackResult',
         '* @typedef {Object} ArbitraryObject',
         '* @typedef {Object} ArbitraryModule',
         '* @typedef {Array} GenericArray',
         '* @typedef {*} Any',
-        '* @param {...*} args Signature dependent on the function',
-        '* @returns {*} Return dependent on the function'
+        '* @param {...*} args Signature dependent on the function'
       ].includes(line);
     });
     break;
diff --git a/test/ui-tests/accessibility.js b/test/ui-tests/accessibility.js
index 4e3d20c1..d243b13e 100644
--- a/test/ui-tests/accessibility.js
+++ b/test/ui-tests/accessibility.js
@@ -3,12 +3,15 @@
 // https://github.com/helen-dikareva/axe-testcafe
 import axeCheck from 'axe-testcafe';
 
+/**
+* @external AxeResult
+*/
 /**
  * @external TestcafeTest
 */
 /**
  * @param {external.TestcafeTest} t
- * @returns {Promise}
+ * @returns {Promise<external:AxeResult>}
  */
 function axeCheckWithConfig (t) {
   return axeCheck(