Today I ran into a strange limitation of level elevations: you can't create a level below -1000cm. That seems very limited to me. Creating a lake or rocket silo will easily run lower than 10 meters. I ran into the problem when I tried to add a maintenance pit for an elevator in a subway station.

Simple wish: extend the negative level elevation to at least -10000cm. I can't think of any reason why this should be a problem.
I temporarily(?) fixed this by editing the Home.xml file where I can easily change the level elevation to -1200 but that is not the way it should be done.