Editing a .plist file on OS X

I am trying to find documentation on how to edit plists. I have found the posts where people have asked the questions, what am i doing wrong here… But i cant find anything that documents how the commands work. everything i see uses “Wait defaults Write…” i dont understand how the command actually functions enough to take these examples and build my own command.

My googling is failing me today, and unfortunately I don’t understand enough to know how to improve my googling for this issue. so hopefully someone can point me to something that can explain it, or can explain to me.

The use case i have for this is to set a default gateway for paloalto global protect VPN clients on our Mac devices.