FreeGameDev

In the track editor videos I saw that there is a simulation mode for objects to let them fall on the ground.

Is there something similar for the starting position? I seem to never get the starting position right which causes the car to “drop” at the start of the game. Especially for bridges!

I am aware this is easily possible by using [Ctrl]+[Left mouse button], but it works only for tracks on the ground. But it doesn’t work if the starting position is on a bridge.

No, there isn't. It would be cool if game did that automatically. Editor doesn't have road in bullet world, only collides with terrain.
I just adjust it by hand, visually the car marker needs to be a bit higher than road.