#Amethyst does this with generic lists, but you need another client to edit the list itself. #Jumble lets you do this with lists of relays, but not users.
#Coracle does both, but uses custom feeds rather than lists for selecting the relays. However, this means you can combine the two so you can see posts from just a certain list of people and only their posts that are on a select group of relays. Coracle also allows you to edit the user lists, but only if they are not encrypted.
