Can Splitwise do currency conversion between multiple currencies?
To do so, navigate to friendship or group you'd like to convert. If you have any transactions with your friend/group that are not already in your default currency, you should see a button to convert all transactions to your default currency. This will update all past expenses to use the new currency.
Please note that if you add additional expenses in the future, those expenses will not be automatically converted – you'll need to come back and click the "Convert" button again, and then those items will be converted at the current exchange rate.