It could be grate to be able to resize two different windows relatively to each other by one mouse move when those windows are 'magnet' to each other.
For example playlist and mixer are magnet ed to each other and by holding 'shift' it could be resized relatively, one gets bigger when the other gets smaller and vice versa. Similar when holding shift and resize two selected clips in the playlist (works also in the piano roll).
windows resize
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