To separate MIDI notes on the grid:
1. Set the Grid value.
2. Make an Edit selection or a marquee selection that includes the MIDI notes you want to separate.
3. Choose Edit > Separate > On Grid.
4. In the Pre-Separate Amount dialog, click OK.
I've been using this feature a lot since discovering it hidden away in the edit menu, but I like to work quickly with keyboard shortcuts and I feel slowed down having to use the mouse to find it in the edit menu. It would be nice if a keyboard shortcut could be added or even if it could be moved to one of the Even Operations Window.
Low priority, I guess, but it should be effortless to implement.