Asking (and answering) questions to which you know the answer

Apologies if this has been asked before, but what are the guidelines here on asking and answering questions to which I just figured out an answer (and I thought could be helpful for others)?

I’m not aware of explicit guidelines on asking and answering own questions. I personally think it’s totally fine when, as you say, it could be helpful to others in the future.

Agreed. Though, since there's no mandatory Q&A structure, you can definitely just post it as a tip you think is helpful.