I just tried out one of the new Key Editor features and noticed a problem immediately: If I cmd + scroll with two fingers on my magic trackpad, the piano roll completely disappears.
I also noticed the behavior depends on the vertical zoom setting. If the vertical zoom slider is above 50% everything works fine. If it is just below 50% the lower part of the piano roll disappears, if the vertical zoom slider it is well into the first half, it completely disappears.
Just to check: when you hold Command and swipe up and down with two fingers (or use the mouse wheel), you’re changing the horizontal zoom, rather than the vertical zoom. However, you’re right that under some circumstances, the piano roll can scroll such that it is completely out of view. It’s not new in 4.0.20 but it is a rough edge we intend to smooth off.
Yes. Command Scrolling changes horizontal zoom. But my problem seems to depend on vertical zoom. I think you might have overlooked my screenshot? It’s not scrolling out of view, it disappears completely including the piano view on the left. Is there a preferred way to send a video to you?
As soon as I drag the slider on the bottom right the piano roll reappears.
It’s not completely disappeared, it’s out of view. I realise there’s not much of a difference in practical terms 
Out of view for me would mean I could get it back by scrolling but that’s not the case. Anyway, if you’re already aware I’ve got nothing to complain 
I find that a simple nudge of the scroll wheel after it has scrolled out of view is sufficient to bring it back.
Not on my system. I see Expression and CC and the ruler moving horizontally without the piano roll reappearing when I swipe with two fingers. Vertically the view doesn’t move at all.
