Custom CSS / JavaScript

For the most part, the default UI works for me. There are a few things that I’d like to tweak. The easiest way would be a way to “inject” javascript and css files on a global level.

Could you add a way to specify locally hosted css and javascript files and inject them into the pages? Then I could do whatever I want with them? For the javascript, depending on how the ui works, you might have to add some sort of page rendered event for the script to hook into.

Yes, please! This would be the easiest solution to let the users change the interface.
The new theme feature is nice, but I think you’ll never be able to change the complete UI with every width, height, padding, margin, whatsoever.
But maybe this can be added to the new theme feature:

frontend:
  themes:
    themename:
      custom_css: mycustomcssfile.css