the 'view' key.

[jens]

You can change the camera mode by clicking of LT, which will allow you to move vertical. Another tip is that you select an object and press F, this will focus on the object and also move the height of the grid to the base of that object. So by using F you can quickly move around in a level and change height too.

You can also duplicate by holding D only and move an object, then it will duplicate as soon as it moves, so really fast for when for example build a wall for a room.