Pretty sure that’s for the Power switch that the Nomad uses
Those four pins are
“AUX 24V INPUT” (2 pins) and “AUX ON/OFF” (2pins)
And before @Vince.Fab’s post above I had never even considered that they were for the Nomad power switch. Ha.
@Julien coming through with the schematics!
Another thing to note is that its functionality might depend on the firmware installed. A shapeoko board powers up when the PS is connected but the Nomad needs that switch plugged in and used to power on/off. (2.4)
I can double check when in a couple days when I’m back to the machines. Also Carbide3d support might have a more concrete answer.