ALT+ Up or Down keys.
Take note that the move is absolute, not relative. Meaning 'up' is up, not the higher numbered track. So if the audio is already on A1, there's no more 'up' for it to go, and any linked video clip will not move. You'll need to select just the video portion for the Nudge to work in that case.
b. ok, (didn't know it worked like that, but it can be "adapted" to my liking by locking tracks (or unlinking audio & video))