Yes. Once you have registered one Global Gift Card you can register the second one as well through your Redemption Overview in the bottom of the screen by clicking "Add more Global Gift Cards".

Please notice! Some variants of The Global Gift Card may not be redeemed in the same order. In these cases the most recent Global Gift Card you enter will become the active one, and the other Global Gift Card codes will be removed from your balance. You can still redeem the other Global Gift Card codes by registering them anew.