Aircraft configuration UI screen and FLTSIM config keys

I see a lot of third-party aircraft do not have very polished presentation inside the Aircraft Configuration screen. Cabin, Gear, Engine, Instrumentation and Additional Information are commonly blank, showing just -.

My understanding is these details inside the aircraft.cfg file in the various FLTSIM sections but I have only found the following keys ui_powerplant_specifics, ui_instrumentation and ui_additional_information. What are the required FLTSIM keys for Cabin and Gear? The MSFS SDK is quite unhelpful here and even the CFG Parameter Index is of no help.

Some aircraft even have partially populated UI elements.