Well, I am not sure if you can edit this somwhere. I know there is an option to edit the size and type of the luggage loader, but that does not exist for the stairs. As stated in the Manual, it depends of the type of airplane, and the parking. Not sure if you could edit it somwhere when you edit a parking place. Mabe umberto can help here. Or mabe it's something they could add later as an option, like the Luggage loader type a vertain staircase you can select...