The sim does have SIDs and STARs in its database, but the internal language used to define them is somewhat simpler than the situations one encounters in real life, and I don't know if any provision has been made to specify transition altitudes. I'll have to look into it. As it is I still find the whole arrangement of transition altitudes in the UK and Europe to be very confusing compared to the US; I've figured out that Heathrow is 6000 and Charles de Gaulle is apparently 4000, but that's it.