How to lock the vertical axis when placing imported objects?

All imported objects seem to be “conforming” to the terrain… that is, their vertical axis is being changed so they follow the terrain (how you would expect for a car for example). But for lots of other objects, you want them to remain vertical. Like imported trees, or houses, or lamp posts.

But I have been unable to lock the vertical axis. Saw official videos on Youtube, etc, and didn´t find a way.

Right now this feature is only integrated in Twinmotion urban furniture library.

have the same problem

This is a problem when I want to place custom trees on sloping terrain.
They should be perpendicular as with the Library trees.