AR Transaction Header Level DFF to use in Account Rule as Source of value

Summary:

Is there a way to use AR transaction Header level Descriptive Flexfield as the source of value in Account Rule in Receivables?

As of now, when trying to search for the Source in Receivables, the Header DFF from AR transactions, the header dff is not available in search. The only available values are the Transaction Line DFF.

Content (required):

We need to get the value from Transaction Flexfield:

The below screenshot shows the flexfield on the source is Line level only. No header dff is applicable to select.

Since we need to get Contract Organization, we need to know what flexfield is being stored in the Source: Transaction Line Flexfield Attributes in the Account Rules.