With the introduction of FSX back in 2006, the possibility to add conditions to the display or behaviour of scenery objects built with the new SDK was not offered anymore. „Tweaking“ the asm-source code as being practised with FS2004 SDK generated objects is not possible with the FSX SDK. Even simple things like the implementation of seasonal variants of an object, that automatically changes according the current season in FSX, has forced the developer to use the old SDK (including transparency issues concerning textures when used in FSX) or to write a setup tool that manipulated the files before running the sim.
This has motivated me to study the SimConnect SDK as this was the only means of controlling objects within FSX. A large subset of SimConnect API function calls are targeted to control dynamic AI-Objects like airplanes, etc. But of course, you can use it to display static scenery objects as well, i.e. AI-Objects that do not move. These objects can now interact with their environment by accessing internal simulator variables. However, to trigger these interactions you are limited to the predefined variables as stated in the FSX SDK. Unforntunately, the use of custom local variables for each object is not supported as far as I know. So basically, to control your object, you have to „hijack“ writeable simulation variables, that only affects that object and not the simulation in general or other objects. The list of possible candidates of those type of variables is very limited, but there are some available and this paves the way to enable conditional display.