Prefabs are implemented in World Builder, and here is some confusion question. We can use sloped blocks in prefabs? So, if this sloped blocks will be put by world generator under surface of ground, water or lava, we will have an empty space:
It’s not possible to have ‘overlapping’ slopes atm. I don’t think the engine supports this (Just like stacking two different slopes on top of each other)
Perhaps, it can be not architectural changes. Devs can makes one unique type of block, which will contain information about combined materials. Like a shelf. But it’s a crutch and I don’t imagine, how it is difficult - to put this idea into code.