The admin lock has been in there for a very long time. Cfg always starts in lock mode. When you unlock, several features are made available, including:
- Ignoring the hide_game options so that all games display
- Allowing the Hide Game option value to be toggled in the options menu
- Enabling all the functions disabled via the simple option and the options simple has control over (install, remove, options, format)
Thus, it is essentially a way to allow people using Cfg with it's child lock functions to temporarily disable them, including hiding selected games from the kids so that only you can launch them. The unlock password is settable in config.txt via the admin_password option, the default for which is BUDAH12 (i.e., B-Up-Down-A-Home-1-2).
The way to enter the password was always to hold the option button down or to assign the unlock action to a button through config.txt. Those methods still work, but it can now can be done by the menus too.