I’m not sure how that’s encoded in AIRAC, but I’d guess it is not airport specific but rather airspace specific.
The transition altitude is important for departure/arrival and center controllers, so I’d assume the TL to change from one airport to another would be quite confusing in between of them.
I agree they should somehow figure that out, it is probably provided with the data.
For the A32NX you can set transition altitude via MCDU, but ingame ATC won’t care - especially annoying for GA in Europe where you state for longer periods between the actual TL and the default of 18.000 that ingame ATC assumes.