I am finding that when using Revenue Field Mapping, only values from the items sublist are able to be mapped to the revenue arrangement. Is there a workaround to this, or some other method to source values from Billable Expenses/Items sublist to the revenue elements using revenue field mapping?

what you are mapping here are transactional line level fields, thus item record/billable expenses is not part of it per se. think more sales orders vs items, you are linking source transaction to revenue arrangement, that is the point of revenue mapping

Thanks for the response - the invoice being created is the source transaction for the revenue arrangement, I may not have made that clear. Your explanation makes sense, thanks for confirming revenue mapping can't be used as I was attempting