Key command for 'Ext' and 'Mix' in the control Room?

I wonder if a key command can be assigned to switch betweeen ‘Mix’ and ‘Ext’ in the control room - for the Main out and Phones?
I only found ‘Select control Room Source’ which cycles through all the cues too and doesn’t work for Phones. Am I overlooking the obvious or does it not exist?

I’m on PCs with Cubase 11.