UI Icons CKEditor 5: update icon

This code is highly 'inspired' from Media Library. So I will refer to it for comparison.

I guess there is 2 ways:
- CKEditor inline menu showing the Icon settings form directly when selecting an inserted icon (like currently the url link if set)
- Selected inserted icon > click the icon toolbar item, open the modal with filled values from the selected icon

Both looks like they need a bunch of work.

I think the complexity of a full 'Settings' form handled directly as CKEditor inline menu require a lot of js on CKEditor Plugin side, which I don't like because it's hard to test. Unless I am not aware of an easy and fast way to test the JavaScript, I am not comfortable with slow Drupal Functional Tests or Nightwatch JS.
In Media Library there is multiple CKEditor plugins and work to achieve it with 'only' align and display selector.

The second option need to send and receive values from Modal, not sure how to achieve, to investigate...