versed atlas
If you are familiar with quake modding , using trenchbroom + qodot plugin is a pretty good workflow
Making it whole in blender works too, but in my experience switching between testing and editing will be slow
For blocking out level you can use CSG nodes, or godot-ply plugin. This allows fast switch between testing and editing level. And after you get the shape of level you can then export it to Blender
I personally uses godot-ply
