If your in pmshell you’ll need to use the following escape sequences to get back to the “Connect to port >” prompt if for example you want to connect to different serial port. If you weren’t confused enough, if you are connecting via SSH you’ll need to use an extra ~ before those escape sequences so the ~ isn’t interpreted by your SSH client, it needs to pass through to pmshell.

Shell Commands:
~b - Generate BREAK
~h - View history
~p - Power menu
~m - Connect to port menu
~. - Exit pmshell
~? - Show this message

I’ve noticed on occasion that I need to be fairly quick with the keyboard strokes or pmshell will just pass the characters through to the device connected to the serial port.

Cheers!
Image Credit to Michaelaw