Sidebar fixes

Fixes #13215 

* when editing a dropdown, but not changing anything you end up in an ugly state
* the hover-over state for the subscribe and other buttons are veeery subtle
* the collapse button needs some sort of hover-over state
* the reference gets shortened. It always got shortened. Not an issue with this in particular.
* the minimized sidebar is not functional. The copy button doesn't do anything
* looks all funky in safari (not for me)

See merge request !2736