There does at least seem to be a convention being used here, in that it’s generally
<aircraft_prefix>_EXT_CHOCKS
etc. So LNG for Longitude, and similar prefixes for the others. But you still have to go to the trouble of finding out what they are, and sometimes they don’t follow the convention, and some aircraft use the UNKNOWN prefix for whatever reason.
The thing is this: 3rd parties tend to either not care much about cockpit builders / Spad / AAO users, in which case you’re just going to have to figure it out for yourself and some stuff may just never work, or they do (a bit) and publish a guide for you - FlightFX is good at this, for example.
For most users, and most developers, these are ‘under the hood’ concerns. If you were using my software you probably wouldn’t care which .NET APIs I used, unless you were trying to plug something in and I supported that, in which case I’d have documented it for you. The problem with MSFS is that it supports plugging stuff in, but most users don’t ever do that, so most 3rd parties don’t spend much time on it for those who do.