> Similarly, if there are any pointers to references on some other data structures in editors like TECO, QED and E, I’d welcome them as well.

The classic is "cookbook for an emacs" but it's from 1980 https://dspace.mit.edu/handle/1721.1/15905

There's also this that's 25 years more recent but 16 years old: https://ecc-comp.blogspot.com/2015/05/a-brief-glance-at-how-5-text-editors.html

And this: https://nullprogram.com/blog/2017/09/07/