Can we add Identifying PO field as accounting condition source?

Summary:

User require: when identifying PO is not null for prepayment, then identifying PO’s header DFF(project) derive to project segment accounting

Issue: we cannot find this condition source.

Besides, solution design is user enter identifying PO but not really match this PO in line. As prepayment is not pay for certain PO line but pay in a whole. So user will only mark this PO number in identifying PO

Content (please ensure you mask any confidential information):

Expected account rule:

Source: Purchase Order Header Flexfield Attribute 9

Condition: if identifying PO is not null

Issue: cannot find this identifying PO source in condition