I think it would be much easier to do playback editing if windows could be "snapped' to each other. For example, if I want how my bassline sounds with one particular synth, I'd pull up the synth in the piano roll editor, then "snap" the B+B editor to it so that I could see both and both would play when I hit the spacebar. I'm not sure if Qt would let you do that, but I think it would be much easier than muting the other tracks, then toggling between the three windows after each change.
God Bless and good day
God Bless and good day