Thanks for the reply, reading the card,
Is that a changing selection of a fixed one? If fixed, you could select the polygons, then invert those (U~I) and create a new selection.
Nodes are, so far I can tell, mainly targeting "Capsule" development. From my point of view, it is a Technical Director option. I do not see it as a target to replace the modeling tools. (I put an equivalent of IMHO in each time to clarify that this might not be the official idea.)
Tutorials:
https://www.cineversity.com/vidplaytut/scene_nodes_-_technology_preview_distibutions_cloning_with_nodes
I have taken a three-volume course from Core4D.com, which a colleague did. I can't find it in the store currently. Perhaps ask.
https://www.core4d.com/ipb/store/
All the best