unable to assign an account rule at segment level for Maintenance expense

Summary:

While we are creating requisitions and purchase order from maintenance and receiving them, oracle issues a direct delivery into work orders. When that happens for Costing SLA the below accounts are hit

Maintenance Expense Dr

Receiving Inspection CR

Since our work orders are POET based, we want to override segment level Code combination values for maintenance expense. So we created account rules in costing based on project source fields. When we go to rule set - Delivery into Maintenance and choose Maintenance expense account to add the account rule at segment level, the account rules are not coming in dropdown LOV.