Unlike SimVars, XMLVars are specific to the aircraft model so, depending on the developer, will change from aircraft to aircraft. You can dig these out of the model browser using developer mode in MSFS.
Using the model browser you can also traverse the interior.xml file to establish the Part_ID. In many cases this has not been set by the developers. To get around this you can extend the interior.xml file with you own and add the Part_ID in the relevant Node.
You can check the lists I have created at https://flightsimhangar.co.uk