Amnesia Partikel und Monster

[Mudbill]

You might not be able to disable the billboard directly, but you can disable a light that it is attached to. Create a light in the entity that has a 0 radius (to make it invisible), but attach a billboard to it. Changing the properties of the light will instead change the properties of the billboard because it is the only thing visible.

I haven't tried this in the Model Editor myself, but I use it in levels and I know it works. I can imagine it would work for in-entity billboards/lights though, if done with above stated method.