My personal desktop app Pretty Good Apps has had a multi-account option for a long time. Also has a feature that shows you a list of relays used by your follows list, ranked by number of users of each relay. I may be the only person who uses it though. Still pretty buggy. I wouldn’t recommend it unless you want to play around with Curated Lists, which I think is pretty cool although it needs better UX. Which is why nostr:npub1p2uwv7qme2u92y2qcpqqvafhkkqsxfrrnz8m79lm60v4005s7vuqnexr0s is rebuilding it!