It’s perfectly fine to split the transactions into two files according to currency if that fits into your file structure, however, TTI’s worksheet supports multiple currencies to complete all transactions in one worksheet (unless your client has more than eight accounts).
If cash is transferred between the currencies, it’s generally easier to manage the journal entry in one integrated transaction in one worksheet.
In addition, the Worksheet tab can be filtered to show transactions for only one account (or currency, etc.) for review purposes, and the results tabs can be similarly filtered and/or provide standalone results by account for detailed review.