The editor uses UI.js that is quite old and not maintained (I guess, no commit for 3 years)...

What is your plans about that?

Is it relevant to improve UI.js, like moving to ES modules and classes, or cook some custom elements?
(In this case I can do it, in fact I already started, and I can start a PR in this UI.js project)

Another option is to switch to an already made component library.
I'm not such a fan of industry giants like Angular or React, it's way too much effort to get a simple UI like the editor's one...
I tried and used the great Xel custom elements, it's easy, lightweight, modular and libre licenced...
(I let you take a look, and I could also start a refactoring of editor UI with Xel elements...)

This issue exists to open the discussion about editor's UI !
Please explain your feelings about this, maybe write your wish about UI improvments, your needs or the lacks you see...