It's called Profiles, and it's already in the game. Larian could make that clearer and more obvious for players to understand, but the feature is already there. You can even move your existing saved games to other profiles.
Baldur's Gate 3 > Player Profiles > [ProfileName] > Savegames > Story > [Save Game Name (Folder)]
I just tested copying the [Save Game Name (Folder)] folder from one profile to another, and it loaded up just fine.
Yes, it's there but the implementation is goofy and non-intuitive. If you don't use a profile then autosaves from the more recent game will overwrite the previous game. If you create a new character it should automatically create a profile for that character.
