Assigning a shortcut to MIDI notes triggers both on note-on and note-off. Ideally, note-on and note-off should map to the "key down" and "key up" check boxes so that the user can decide which action should trigger what.

No matter what the solution to this problem looks like, it most likely cannot be stateless: For each note-on event, we need to memorize that the corresponding note-off event should not be processed any further and e.g. cause a note-off to be written to the pattern editor. On the other hand, if a shortcut is only triggered by note-off, this note-off should still be processed by other parts of the program that might have processed the note-on event, or that note will keep hanging forever.