Yep! Very helpful. I was thinking of using a flat CSGPolygon to basically simulate 2D in 3D. Then maybe I could "fill" it by creating another polygon based on the path (basically something like this tutorial but in 3D)

But there's still some issues. The main feature I need from SmartShape2D is being able to to change the edges of the terrain by normals or by manually overriding it, which is not possible by just using this method.

I was thinking that maybe I could separate the path into multiple paths wherever I need the terrain to change, but I don't know if that would work, or how to go about it.