That‘s essentially correct: „custom animations and simulations“ are most often implemented using „local variables“ and hence not reported via the official SimConnect „simulation variables“:
https://docs.flightsimulator.com/html/Programming_Tools/SimVars/Simulation_Variables.htm
(If a corresponding variable exists in the first place).
And even if such a customised aircraft would report simulated values (that is, during recording), reacting to such value changes (during replay) is written on an entire different page of the book (same for events).
So if you know the name of the specific „simulation variable“ or IF your aircraft allows to bind the door open/close action to some keyboard or hardware button („event“) - let me know!