First up, you apparently haven’t implemented ALT menus. aka ALT + F etc… I don’t usually need it, but occasionally the mouse isn’t hooked up or something and it’s nice to be able to just use the keyboard.
Secondly I had an idea, the ALT key could be useful for in “locked” mode to be able to ALT click/dock undock windows. Then you wouldn’t accidentally rearrange the UI but you could deliberately very easily.