Keyboard shortcuts: Open tag list does not work on Linux (Ubuntu only?)

Follow-up from #2705

> I've been testing on Linux and the only one that doesn't seem to be working as expected is the open tag list Ctrl + Shift + U. If you are focused on the editor this doesn't fire while all others seem to.

Ctrl + Shift + U seems to be a [global shortcut](https://superuser.com/questions/358749/how-to-disable-ctrlshiftu-in-ubuntu-linux) on some versions of Linux.

Reproduce the Ctrl + Shift + U shortcut while focused on the editor on Ubuntu, then trace the keyboard-shortcut handling used for opening the tag list. Compare its behavior with the other shortcuts mentioned in the issue and verify that the tag list opens without conflicting with Ubuntu's global shortcut.

Written by the indexing model from the issue text.