@LSlowak I am currently using the midi editor a lot, and here another little suggestion:
When 2 notes of the same pitch are adjacent, it is hard to tell. They look like a single, long, continuous note. Especially if they touch each other on a grid line. Is it possible to use maybe a different color for the dividing line between the 2 notes? Or maybe a slightly thicker or darker line where they touch each other? It’s not needed a strong contrast, just a bit, so things will keep clean.
A similar request is also for overlapping notes (partially or completely): the note hidden by the note on top is currently competely hidden, not visible at all. But it should be visible that a note is being covered by another one. Again, it’s enough a soft contrast to reveal the hidden note.