You really can search for it in the doc. "man zshexpn" and search.
Nuts. It's there as you say, but my favorite online version of
the manual can't find it. I wonder how much grief that's caused
me? Maybe my 'search for syntax' idea is obviated because it's
just this particular HTML version that can't do it. That's
irritating.
https://zsh-manual.netlify.app
... very attractive and easy to read but ...