There is already a shortcut for what you suggested: Ale-Left Arrow. It nudges a note left by 1 Ms. But you'd have to zoom in all the way for each note separately in order to left justify them all.
Looking for a way to take 6 or 8 existing notes not starting at the same time and match their starting points all at once:
Ie:
-------C2
---G1
-----------E1
C1