Serious Sam 4

Serious Sam 4

Custom maps, mods, skins & campaigns
Discover and download custom maps, character skins, weapon modifications, skins, enemy modifications, campaign mods, and much more.
-Serious Sam 4 Editor Help- (Making Tunnels)
Is there a way to "carve" tunnels with brush into polygon mesh like in Unreal Editor?
Or do I have to sort of "build around the "tunnel"?

So what I need is a tool to edit the polygon so that the selected area gets removed, but otherwise the polygon stays intact. For making windows, tunnels holes etc.

I'm stuck for now :(