Also it'd be nice to have something that is more spatial. A famous memory technique is remembering where things are in space[1], but I've never seen a code browser that works spatially. (I have no idea how to actually do this.)

[1] https://en.wikipedia.org/wiki/Method_of_loci

Who remembers the Occam folding editor (1983)? This was the first time I saw this kind of outline-based navigation for code: https://www.transputer.net/tn/03/tn03.html#x1-30002