Hi.
There is a cheat method of creating clip volumes. Although as i said its a cheat method.
You can use a mesh that is hidden but still force it to block light / cast shadows.
The only problem i find using this method is that if you want to see it in the editor it sort of blocks out visuals because its a solid block… and if its hidden you might forget where you put it.
One way i found to mitigate this is to create a material that draws it as a wireframe… and set it to be only hidden in game.
This would make a great addition to the engine i agree