Food4Rhino

Mesh NGon Methods for Grasshopper and Rhino 6: NGon Create, Vertex, Edge, Face Adjacency queries, Subdivide, Planarize, Transform, Utilities.

Essentially it is a plug-in for polygonal meshes.

Add library files to: ...\AppData\Roaming\Grasshopper\Libraries and unblock them.

Please be sure, that you unblocked all the files: right click on each .dll or .gha file and if there is an option "Unblock" - tick it.