You can use the action Destructible - Set elevator height to define at which height it is, and use Destructible - Close walls to "open" the elevator.
For instance... The elevators has four invisible walls around it - the south one, the north one, the west one and the east one.
If you close the north one, the upper side of the elevator will be unpathable (this prevents the unit from climbing walls with the elevator lower than the wall).
There are more uses but I don't know much, so better don't say =P