It would be nice to be able to highlight keys on the piano roll. I have some percussion instruments that only trigger on a few keys, so this would make it easier than blindly stabbing around on the keyboard in order to find the triggers.
Use Drum Editor and Drum Map, please.
Or give us the ability to do it in the Key Editor. Saves us having to open and close a new window while we are already in the Key Editor. After all, good workflow means as few clicks as possible.