Project Attributes in Receivables SLA

Summary:

I'm able to use a project attribute in AR accounting rule, although successfully validated but is not appearing in the Journal Line Rule Set to assign to override in create accounting process.

Step 1: FSM > Financials > Receivables > Manage Accounting Rule

Create new accounting rule, use Source = Expenditure Category Descriptive Flexfield Attribute 1

Validate, Save and Close

Step 2: FSM > Financials > Receivables > Manage Journal Line Rule Sets

Navigate Invoice Default Receivable, but this new Accounting Rule is not appearing in the list of values. See attached screen shots.

Is this possible at all?

Can you also point me in the direction where I can take a look at supported project accounting attributes in Accounts Receivables SLA?