Or, less ergonomically, the general rectangle-editing commands built into more powerful code editors e.g. Emacs.
With these, simple but fairly pretty box+line+text diagrams can be inlined with your source code comments. This unification may help in the perennial struggle to keep software architecture and source code reality in sync.
There are not many other ascii diagramming tools
(ascii to diagram)
Typogram https://code.sgo.to/typograms/#installation
Markdeep https://casual-effects.com/markdeep/
svg bob editors https://ivanceras.github.io/bob-editor/ https://mbarkhau.github.io/asciigrid/
Ditaa https://ditaa.sourceforge.net/
Goat https://github.com/blampe/goat
Protocol https://www.luismg.com/protocol/
(dsl to ascii)
https://diagon.arthursonzogni.com/#Sequence
https://textart.io/sequence
https://weidagang.github.io/text-diagram/
https://diagwiz.io/playground/
There is another, related class of tools, and that is graphical editors of the Unicode box-drawing characters:
https://github.com/lewish/asciiflow
https://github.com/tbanel/uniline/
Or, less ergonomically, the general rectangle-editing commands built into more powerful code editors e.g. Emacs.
With these, simple but fairly pretty box+line+text diagrams can be inlined with your source code comments. This unification may help in the perennial struggle to keep software architecture and source code reality in sync.
https://d2lang.com/ is really nice.
Also I used to use https://swimlanes.io/ before d2.
Also,
https://pikchr.org/
Needs to have a '+' and the elbows and T intersections.