I have a 61 keys controller and would find it great if I could “resize” the onscreen keyboard to exactly the size of my controller keys. Means, the onscreen keyboard doesn’t show the full key range from 0 to 127, but I can define it to show for example 36 to 96. Another step between would be to grey out the upper and lower ends.
Somewhat related to this, I found myself at one time having to switch frequently between main keyboard and onscreen keyboard. Would it be possible / desirable to have both active at once?