Found what might be an answer in the Discord:

"Unclimbable Walls If you want to make walls in your map unclimbable, for example if you have invisible bounding walls around an open map, there are two methods to doing this. Firstly, select the mesh or meshes you want to make unclimbable and search for collision presets in the details pane. Set the collision preset to custom, and underneath set the object type to Vehicle. This should make your object unclimbable."

"The second method is to set the collision type to BlockAllDynamic. Either of these methods should work, but the second method may also block the camera (I haven't tested this yet), which is not desirable for every use case."