Select Previous Region/Cell on Focused Track ←
Selects the previous region. The selection is _circular_. If the first region on the track is selected the command will wraparound and select the last region on the track. OK by me.
The specific command is not documented any more than its entry in the list of Global Commands.
To perform some edits on regions, you must first select the regions. You can select one or multiple regions, select regions on different tracks, and quickly select muted regions, overlapped regions, or regions meeting other criteria. Selected regions appear brighter in the Tracks area than unselected regions.