IIRC you can label the audio I/Os in the macOS audio-MIDI-setup.app. However there’s no import/export for the labels. GP derives these labels and shows them at least in the audio options dialog an further on when hovering over the port pins in the wiring view. I think there have been some limitations and side effext when I tried.
I’m not at my mac at the moment, I will re-check this evening (if I don’t forget to remember…).
Or was this only for aggregate device?