You’ll find the pin layouts in document “Jetson Xavier Developer Kit Carrier Board Specification”. You might have to go here, then login and go here again:
Search for “Xavier Developer Kit Carrier”. You will see the Specification file listed there.
Input pins are grounded to activate. A single pole single throw momentary normally off switch does the job (whew, that’s a long description for shorting two wires together).
I’m unsure if standard headers on a PC chassis work with this or not, but it is possible (I’ve never researched it…but PCs don’t have recovery mode, so it can’t be a perfect match).