I'd like to select and group the primitives I've highlighted in the picture above, but not sure how to do it from a procedural standpoint (the size of the grid, as well as how many rows and columns it might have, could change down the line).
There's obviously the 'unshared edges' option in the group node, but not sure how I'd then go about excluding the edges I didn't want from thAT selection (if that was indeed the way to approach it, which it probably isn't!).