No plans at this time, but it would be nice to see a Table of Contents. Right now an author can embed things like this into their own notebook but no plans to see it for all.

not sure i understand what your second sentence means.

Right now an author can embed things like this into their own notebook but no plans to see it for all.

You create a table of content using markdown in the first cell, it will be rendered on nbviewer.

ok. so you are suggesting is manually creating the TOC?
i suppose supporting the nbtoc extension in nbviewer is probably more complicated than i presumed.

ok. so you are suggesting is manually creating the TOC?

Yes, for the time beeing.

i suppose supporting the nbtoc extension in nbviewer is probably more complicated than i presumed.

Probably not that complicated, but it need to be done, and everything takes time.
As for none of us developing nbviewer is a full time time job, most of things don't happend unless someone else comme and implements it !