I like to use the Msh2Coll option in the Modeling Mode to apply collision to props I’ve imported. It seems semi-tedious to go through the process of applying collision to so many assets repetitively. I’ve tried to use this while selecting multiple assets, which did not work. Correct me if I’m wrong, but as far as I’m aware there is no way to add collision to multiple props at once like this, and it would be nice if we could.
Maybe I am wrong, but I think you are adding collision to the individual actors within the scene. Maybe use the mesh editor to apply collision to all of the same actors at once, aka the mesh itself? Because that way the mesh always has collision saved and you only do it once per mesh.