I'm used from Windows to press alt+up to navigate to the parent folder in the file explorer. When I do this in the Unity file manager, it moves up but it also opens the HUD, stealing focus from the file manager. Is there a different shortcut for the navigation or another workaround?
If you keep pressing Alt a little bit longer there will not be any conflict.
As alternative, you can:
Change the HUD's use of the Alt key:
Change shortcut keys for Nautilus: