Hide Subrows for Row    ⌃⌘←

Hides all of the subrows of the current row. Click on the disclosure triangle. Collapses the expanded view.

The same key command will hide tracks in a Track Stack.

Logic Pro Step Sequencer overview — Apple Support

Step Sequencer is inspired by classic hardware step sequencers that have rows of configurable switches or knobs used to generate repeating musical patterns. In Step Sequencer, you create patterns by editing multifunctional steps in the step grid. Each row controls either a sound (which can be a drum kit piece, a note on an instrument, or a range of notes) or an automation parameter (letting you create automation changes over time in the pattern). Each step represents a definable length of musical time–by default, steps are of equal length, but you can change the length for individual rows or steps. You can adjust a wide range of parameters for individual steps, including velocity, pitch, gate time, and more; and edit pattern and row settings including pattern length, row loop start and end points, playback position, and rotation.

  Flatten Track Stack for Selected Channel Strips

Removes the tracks from the track stack, and remove the stack channel strip from the mixer. NB that when you remove a stack the channel strip _moves_ to the normal location for an AUX channel or a VCA.

I assume that there is a separate command for this when working in the mixer since there really aren’t any tracks to work with.

In the standard configuration of Logic Pro X the ‘Flatten Stack – ⇧⌘U’ command has no overloaded commands, so you could assign the same keyboard sequence to the ‘Flatten Track Stack for Selected Channel Strips’. I have done this and don’t see any particular downside. The same can be true for ‘Create Track Stack for Selected Channel Strips — ⇧⌘D’.

  Create Track Stack…    ⇧⌘D

There are two kinds of track stacks — Summing (bus/aux) and Folder (VCA). Logic creates a track in the Arrangement area with the selected tracks included. All the tracks are routed to the same AUX channel, or controlled by the same VCA. It is a very convenient way to get AUX tracks and VCA tracks into the Arrangement area. Allows you to move the positions of the channels/VCA in the default mixer view.

I use track stacks (summing) all the time.

Nesting of track stacks is not possible. If you want a number of Summing stacks to be in a Folder stack you can’t do it. You can place all of the track stacks onto the same VCA, create a track for the VCA, and move the VCA track next to the summing stacks.

Create and edit Track Stacks in Logic Pro — Apple Support

You create a Track Stack by selecting (adjacent or nonadjacent) tracks in the Tracks area. Nonadjacent tracks move so that all tracks are grouped together in the Track Stack. Both types of Track Stacks can contain any combination of track types as subtracks. A folder stack can also include summing stacks as subtracks.

Logic Pro X keyboard command of the day. #LogicProX @StudioIntern1

  Open/Close Track Stack

Opens or closes the track stack with current focus. Unfortunately this is “global” for the main window. You cannot have a different state for a track stack in different screensets.

⇧ SHIFT – ⌃ CONTROL – ⌥ OPTION – ⌘ COMMAND