Just assign a shortcut to this PLE.
Hitting several times it expands more the automation lanes.
To go back I just hit the current Workspace but that depends on how you have configured it. Other ways are by Undo zoom or Hide all automations or by zoom Mem and Zap.
How to close lower zone (currently just can toggle it) if you use Touch Portal or Stream deck,etc:
Set a left click command on this position:
I use Touch Portal and it´s very useful to combine this command with other Cubase macros in a single button.
Combined with “show/hide lower zone” command it can be used to just open the lower zone.