I am in a similar situation like the user here, in need of a customer statement showing transactions in FOREX - though only in the app and not via API - which requires TransactionAmountMultipliedByNegativeOne to function correctly.
The other suggestions made in the post (among them using Advanced Queries) don’t work because they usually make only use of the reporting currency and don’t show foreign currencies.
Is there any chance you can implement TransactionAmountMultipliedByNegativeOne in customs reports?