When logging into Service Studio, it seems to remember the last 6 environments you connected to.
If you have a client with 5 or more environments, a personal environment, 2 partner environments, this list is never complete since only the last ones are saved. Either allow for a bigger history (last 20 for example), or allow for a complete management of environments where you can predefine the ones you want. This could include hostname, username, password, color coding, etc...