GMod had a much lower node limit when I created and released the map. Covering the entire playable area with ground nodes was already a big challenge, and unfortunately it left me with no room to spare for other types of nodes.

The node limit has been raised since then, but I'm no longer updating this map or working with GMod in general. If you look around on the workshop, you might be able to find an edited version of the map or an improved nodegraph that does contain what you're looking for.