[nlawalker]

That's what https://yaml-multiline.info is for! I know the author's on HN, I hope they chime in here :)

Amusingly, the Stack Overflow answer you linked in your contribution is the second result in a Google search for "YAML multiline string" or the like, after yaml-multiline.info; the two combined appear to the canonical resource on the web.

[stevage]

Heh, not sure if you realise, but that website was inspired by my SO answer. (I'm credited at the bottom).