All of these suggestions are nice, but when it comes to efficiency, they're terrible compared to the feature I'm suggesting. Why would I need to go into a whole refil when I can just click a drop window (like the snap-to-grid) and highly all the piano roll keys of a certain scale & key?
And the suggestion to have the "note correct" function is even worse I think. Then it teaches to just play random notes lazily and they'll be in key. It'd work well as a live performing device for sloppy keyboard players (like myself, who is a drummer/guitar player), but not as an audio production engineer.