I love these railroad diagrams and they were in lots of documentation when I was a programmer at IBM.

This cool online tool[0] can make them from EBNF[1] syntax, something else invented and used extensively at IBM.

[0] https://bottlecaps.de/rr/ui

[1] https://en.m.wikipedia.org/wiki/Extended_Backus%E2%80%93Naur...