Is there any way to undoing boolean union? I mean I want to separate two solid again. But I did lots of command after boolean union, so I can’t use undo. Is there no way to make it separate again?
There isn’t a one-button function to do that, no. You can extract surfaces and untrim those, then join back into the original objects.
I see. So there is no one-button to do that, thanks a lot!
Depending on the complexity of your booleaned objects and just how far down the road you have proceeded from the union, undoing back just before the union and redoing may still be the most efficient way out.