I was talking about Star Trek IV in another sub, and looked at some H.D. stills of the scenes in the Federation Council chambers. In the closing session, Dr. Chapel and Chief Rand make cameo appearances. And they're wearing UFP pins on their uniforms that are only ever seen in the Federation Council chambers or worn by the Federation President elsewhere.

Spock and Dr. Taylor aren't wearing them, and we know that they aren't members of the Council. But everyone else in the galleries is wearing them. This includes Sarek and the President, who are members of the Council. It stands to reason that the people wearing the pins are all Council members. Including Chapel and Rand???

This would also mean Cartwright was a Council member in 2286, but given his senior leadership role in Starfleet, it is not implausible.