Same as for currencies, placeholder DLC achievements can be found inside WillowGame.Default_AchievementUtility.
The real amount of Golden Keys is stored inside the profile.bin file instead of the character save file itself meaning that this slot is in fact not used. This slot is shared between all 4 Campaign DLCs. The following is the current full currency list for Borderlands 2. Developers used placeholder currencies slots for upcomming DLCs but didn't actually use all of them. Placeholder currencies can be found in the game's code.
