Do not create accounting for billable flag change

Summary:

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When a project billing invoice expenditure transaction is set to non-billable, it is creating Supplier Cost Adjustment accounting entries from projects to GL. We do not require any accounting entries to be created when billable status changes, what is the simplest approach to suppress this?

I was looking at creating a new Journal Line rule with a condition that would exclude adjustments for the billable flag being changed, however I am not sure what they condition should be as I do not see an Adjustment Type (i.e. "Set to nonbillable") or an Adjustment Source (i.e. "Invoice Work area") available in the conditions.