Well you as soon as you bind it you can back it up without leaving the game. Once entering the game, as long as you didnt open the options menu or you didnt crash, the binds will still be there. In case you did crash or open the options menu you just used your backed up .cfg and all your binds will be back.
It's also good if you wanna make multiple .cfg files for different things, like if you needed over 9000 keys for choosing your hair and the colors of your armor or whatever.