Close Track Stack ⌃⌘←
Closes the currently selected track stack. I use summing track stacks to work with “stems”, and to help organize the tracks. When I want to work on a stack I simple select the stack and switch the mixer view to ‘Single’. This places the AUX, all the channels that route to the AUX, and the output path from the AUX (mix, sends, stereo out). Very handy.
Folder stacks (VCA groups) provide a simple visual way to control volume, solo, and mute for the group.
Summing stacks work like sub-mixes with inserts and sends.
Create and edit Track Stacks in Logic Pro — Apple Support
You can hide the subtracks of a Track Stack to save space in the Tracks area, or show them in order to record or edit. You can add or remove tracks from a Track Stack, and reorder tracks in a Track Stack (reordering tracks doesn’t affect the sound).