Another thing the ipad GB editor does well is selecting a range of notes vs scrolling. If you want to scroll you just swipe a blank part of the background
If you want to select a range of notes you long tap until the selection box appears and then drag to select a set of notes. Much easier than having separate Selection / Drawing / Scrolling tools.
The other improvement I would request is to add inertia to scrolling and zooming in the Piano Roll (it doesn’t feel right for the windows to stop dead after you swipe, much better to gradually slow to a halt and also allows to scrub / scroll faster or slower depending on how fast you swipe)
Apart from that , congratulations on a good product. There are things which could be improved but over all it “Feels Right” and most things work as expected. Pretty good. For a version 1.0 !