Hi James
Thanks for your ideas. I hadn't thought about using the corner points like this.
Although, I should think more about adding a break to curve or merging curve segments.

I was thinking about adding a new node for selecting sub-objects like edges and faces to use them in filletEdges, blend, offset, inset, extrude, n-sided, network and shell nodes.
Maybe I can add an extra "point" option to it.

One thing I'm not sure about is if is it better to write a "select sub-objects" node and rewrite other nodes above to work with it,
Or, add selection function like "filletCurves" to all of them. (I guess the first one is faster and easier!)