Looking for a User Guide for the remote - not the simple 1-sheet diagram on the Phonak site.
The diagram you’re referring to is the complete user guide. It’s printed on a large sheet of paper and folded into a small leaflet before being placed in the product box.
What is the purpose of the center button?
That button cycles through the various listening programs in your hearing aid(s). If you only have one program assigned, it won’t do anything.