How to add a list of existing tags to the description of a tags panel in Gutenberg WordPress

The puzzle

I'm working on a custom WordPress theme. I've created custom post types and custom taxonomies, some of which are tag style (rather than category style). All is working as it should, and the appropriate taxonomies show up where they should in their matching content types ('show_in_rest' => true).

BUT I would like to add a list of the currently existing tags to the description in the tags block.

Right now, the instructions for tags say: "Separate with commas or the Enter key." I'd like to append something along the lines of "Existing Tags: " and then the list of tags. Ideally, this would be dynamically generated, so that as clients add new tags it would update the list. For the specific site I'm working on though, even static text would be better than nothing.

What I've got so far

I found someone asking a somewhat similar question and tried using the code from one of the responses. I'm taking a modular approach, so I've put the enqueue_script in a separate php file which I'm require_once-ing...

In functions.php, I've got:

...

require_once("lib/gutenberg/tag_options.php");

...

In tag_options.php I've got:

<?php

/**
 * Add a list of available tags to tag panels in the gutenberg editor.
 */
function radicati_tag_options() {
  wp_enqueue_script(
    'gutenberg-tag-options',
    get_stylesheet_directory_uri() . '/lib/gutenberg/tag_options.js',
    ['wp-blocks', 'jquery'],
    1.0,
    false
  );
}

add_action('enqueue_block_editor_assets', 'radicati_tag_options');

And in tag_options.js I've got:

window.onload = function() {

  // This is code I found on the internet, 
  // aimed at creating a custom panel...

  var el = wp.element.createElement;

  function customizeProductTypeSelector(OriginalComponent) {

    console.log(OriginalComponent);
    return function(props) {

      console.log(props.slug);

      // The slug of one of my custom tag-style taxonomies is "topic"
      // That's what I'm seeing in console.log, so I feel like I might
      // be on the right track!

      // Once I get this figured out, if need be I can write custom code
      // for each of my custom tag-style taxonomies :)

      if (props.slug === "topic") {

        return el("div", {}, "Product Type Selector");


        HELP! THIS IS WHERE IT ALL FALLS APART! 
        I CAN *REPLACE* THE CONTENTS OF THE TAG BLOCK 
        (AND THUS RENDER IT NOT A TAGS BLOCK ANYMORE) 

        BUT I JUST WANT TO ADD A PARAGRAPH CONTAINING 
        SOME TEXT, INCLUDING A LIST OF EXISTING TAGS 
        TO THE OTHERWISE PERFECTLY FUNCTIONAL BLOCK!


      } else {
        return el(OriginalComponent, props);
      }
    };
  }

  wp.hooks.addFilter(
    "editor.PostTaxonomyType",
    "my-custom-plugin",
    customizeProductTypeSelector
  );
};

TIA

Unfortunately, the documentation for messing with Gutenberg stuff is still pretty patchy, so this is as far as I've been able to get. I'll admit that my React is equally sketchy, so it's a pitiful combination :laughing: If any of you have any clues to throw my way, I would really appreciate your help!