gSender 0.6.7 Mac comms issue

Hi
Just installed gSender 0.6.7 on my Mac - Big Sur 27" iMac. I’m testing it with a gash Sainsmart CNC 3018 board, but it won’t connect.
I’ve checked the connection with a serial terminal and also with universal gcode sender - all connect just fine (across USB).
I notice that there’s no option to pick a port - I’m assuming that it’s ‘automatic’ and looking for a port that it can talk to with a m/c at the far end. That’s really not a great idea - especially when machines can have multiple ports and may also have multiple emulations running with their own ports that can get in the way.
Is there any way to pick-a-port-of-your-choosing from within gSender ?
Otherwise, looks very professional from an aesthetic standpoint ! (10/10 compared to Mach LOL).
Neil