[12/23/21 update: One new template added that is triangle-based, specifically by taking all the 1-world-unit squares from the unfilled grid template and dividing them into four triangles.] I use pre-prepared templates to make a lot of NEFX maps and I felt it was time to pass them along for anyone else's use.
One of these is used to create many NEFX netmaps, and is a room of 700 1-WU square polygons with pre-textured walls, ceilings, and floors, differential shading, item spawns, and sounds.
Another one is similar but spanning the entire possible map, and may be used for solo maps. Of course, you may want to delete some of the squares.
The oldest one is the same as the second one except unfilled and not configured.