For reference, in regard to idea to dragging Composer to another screen, here is a related post:
In regard to customising colors etc, if you are a web developer, and familiar with chrome dev tools etc, you can go to Cursor > Help > Toggle Developer Tools and then you can play around with CSS etc.
In regard to persisting those changes, even though they could possibly break on subsequent versions, I am not sure if there is a best practices approach or not.
Another user has mentioned a related extension here: