+1 Collapse or minimize layers would be fantastic, you don't really need to see the entire contents of a group during playback. Visually it would be much nicer if you could collapse/expand layers that you don't need to see. Folders behaving like groups in photoshop or a shy layers in After Effects.
It is a good thing to have when you have more layers and we can make all the required layers visible on the screen without scrolling up and down. 100% for it.