How to customize the LinkModal mockup pattern that is provided by TinyMCE

I am trying to customize the default Link modal that pops up on TinyMCE when attempting to hyperlink text. This refers to the Internal Link tab. The behavior that I want to add is having a dropdown with preset rootPaths to restrict the search to. This way users can quickly define up front which folder to search within. I know the tree provides it, but my use case wants a 1-click path for a number of preset folders that we know.

So first I set out to customize the Related Items pattern using this concept:

To extend:

The problem is that I do not necessarily want every interface that uses the pat-relateditems to implement the new behavior.

I also saw that I might want to extend the LinkModal pattern, but when I attempted to do that, I found that the extended version did not call the extended show function when the user taps to insert a link from TinyMCE.

], function($, tinymce, LinkModal, registry) {
  'use strict';

  // first, unregister existing pattern
  delete registry.patterns.linkmodal;
  delete $.fn.patLinkmodal;

  // creating new pattern automatically registers it
    name: 'linkmodal',
    trigger: '.pat-linkmodal',
    parser: 'mockup',
    init: function() {
      var that = this;;
    show: function() {
      var that = this;;
      // customizations here


So my question is, does anybody have any good docs on how to customize the LinkModal?

Thank you in advance for any insights!