Compact track folders in mixer

In the track display area, the option to click to compact or expand all tracks in a track folder is great. Saves masses of screen area.

This suggestion is to add the same function to the Mixer area (but compacting sideways of course).

Variations:
The collapse\expand states in the Mixer and Track display areas could be linked, so clicking to compact\expand in one area causes the same display change to occur in the other.
Or, each display area could have track folder collapse\expand states set independently by the user.
For my purposes, the independent variation would be best, I think : )