Simplest AHK-based Steam account switcher
Just run SteamSwitcher.ahk and double click the username of the account you want active.
To setup the accounts, sign-in (with remember password) and sign-in (log out if need be) into the second account. Now, you should be able switch between the accounts with this application.
Special thanks to lemasato.
Forum topic: https://www.autohotkey.com/boards/viewtopic.php?f=19&t=97701