In the Station Launcher go to Options, then Preferences. In the Preferences window click on the "Startup / Shutdown" category. Check the box for the option "Exit Station Launcer when I play a game."

Next, launch your first account and when you do you will be logged out of the station launcher. Minimize the game instance and re-run the launcher and log into your next account, repeat...

It's not a quick way but it works.