GOG Wallet is available in all currencies available to you after login depending on your current location.
With the new currency implementation, you now have the choice to pay in your local currency.
However, for legal reasons, we cannot mix two currencies in one purchase. So, if you top-up your GOG Wallet in USD, you’ll have a wallet balance in USD and, for purchases made in your local currency, you’ll have a separate GOG Wallet balance in the local currency.
Please keep in mind that funds cannot be transferred from one wallet balance to another (which also means from one currency to another).