If you have connected banks that use foreign currencies, you will see currency fields when you open the transaction details and select Add.
Enter the Foreign amount or the Exchange rate, whichever your bank provides. QuickBooks will calculate the total. The Bank Description or Detail fields will display the transaction as your bank displayed it on your statement, usually with the amount and currency.
If you are using a foreign currency, you can still split deposit and expense transactions based on different account categories and tax. However, you can't split a transaction based on different currencies.