The SAVED indicator in the composer seems to "lie to me":
type something, see SAVED,
then cancel the overlay — or accidentally click outside it — and click New post again: the text is gone.
Bug, or am I missing something?
When you click on New Post it starts a new post.
There is a command that does what you want, in the Menu at the top of the page, Focus on Editor. Probably not a great name, and not something people will know to look for, but now you know to look for it when you accidentally or intentionally click outside the edit box.
Saved does work, if you reload the page while editing, the text will still be there.