It's already 4 years since this was deprecate. Here #12561 you'll find all the info you need to fix whatever is broken

don't agree to comment. "jInsertEditorText" javascript is available with latest stable joomla version (3.9.20). The issue comes with version 3.10 and version 4. (#12561 describes a totally different problem).
So: will there be a replacecment for "jInsertEditorText", a solution or documentation for this or not? Some developer will (at least) need some info if code is deleted and cannot be used anymore.

// An object to hold each editor instance on page, only define if not defined.
Joomla.editors.instances = Joomla.editors.instances || {
        /**
         * Editors MUST register, per instance, the following:
         *
         * getValue         Type  Function
         *          Should return the complete data from the editor
         *          Example: function () { return this.element.value; }
         * setValue         Type  Function
         *          Should replace the complete data of the editor
         *          Example: function (text) { return this.element.value = text; }
         * replaceSelection  Type  Function
         *          Should replace the selected text of the editor
         *          If nothing selected, will insert the data at the cursor
         *          Example: function (text) { return insertAtCursor(this.element, text); }
         *
         * USAGE (jform_articletext is the editor id)
         * getValue:
         *      Joomla.editors.instances['jform_articletext'].getValue();
         * setValue:
         *      Joomla.editors.instances['jform_articletext'].setValue('Joomla! rocks');
         * replaceSelection:
         *      Joomla.editors.instances['jform_articletext'].replaceSelection('Joomla! rocks')
         *
         * *********************************************************
         * ANY INTERACTION WITH THE EDITORS SHOULD USE THE ABOVE API
         * *********************************************************
         */
    };

You should use the new API: Joomla.editors.instances['editor_id'].replaceSelection('Joomla! rocks')

I'm using this half-assed, paranoid(?) code in all of my xtd-plugins (select/enter something in a pop-up and insert via button). From a time when first 4-dev "releases" came up and I tested my dinosaur J3 xtd-plugins with some editors on both platforms:

/** Use the API, if editor supports it **/
if (window.parent.Joomla && window.parent.Joomla.editors && window.parent.Joomla.editors.instances && window.parent.Joomla.editors.instances.hasOwnProperty(editor))
{
	window.parent.Joomla.editors.instances[editor].replaceSelection(tag);
}
else
{
	window.parent.jInsertEditorText(tag, editor);
}

@ReLater im wondering who could ever wrote that paranoid code, oh wait: #14935 (comment)

Ah, f'ing auto correction of my keyboard. I wanted to type "paramount" not "paranoid" ;-)

For me it looked like one of my own paranoia what-the-hell-is-really-needed IF structures reassembled from diverse code snippets found on stackexchange ;-)

if (good && !bad)

No harm meant. It's brilliant code... because it works ...

@ReLater no worries I was trolling myself 😎