What code navigation features are part of literate programming and would be appropriate for inclusion in this dissertation?
Do any of those actually implement Literate Programming as DK intended? As in "you can move the code around to wherever makes most sense for your narrative"? As best I know, almost all "literate programming" today is just the intermingling of code and text blocks (e.g. Docco et al) in the same order the code would have to be anyway (i.e. there's no TANGLE, only WEAVE.)
That could be.
Are there any novel navigation approaches that have fallen out?
In one of the "internals of TeX" videos, Knuth mentions how when he got to a particular section of the code, he had to move to a larger desk (yes, desk) so that everything could stay in sight. If you're comfortable with such a style of programming, paper gives you a lot of freedom: you can have a very large number of (literal) "tabs", cover parts of pages, make throwaway annotations while reading, etc.
Anyway, as far on-screen navigation goes, with pdfTeX there are hyperlinks: you can navigate from the mention of any section to its actual code, and backwards. (E.g. start at section 4 http://texdoc.net/texmf-dist/doc/generic/knuth/tex/tex.pdf#p... and go to one of the mentioned sections, and back from them to 4.) (It would be nice for there to be even more hyperlinks, but no one seems to have implemented them as Pascal isn't exactly popular these days.)
And to answer your question most concretely: the (recent) online version of the Literate-Programming book Physically Based Rendering: From Theory To Implementation has some innovative navigation aids IMO. (Random "page" / section from the book: http://www.pbr-book.org/3ed-2018/Camera_Models/Realistic_Cam...)