Automatic release of parked invoices in flexible workflow

Good day,

We currently have a requirement to only have supplier invoices without reference to a PO go for approval and all supplier invoices with reference to a PO should be released automatically. We thus activated the flexible workflow for supplier invoices scenario WS00800303 (Workflow for parked invoice as complete). We created a custom starting condition (Supplier invoices without PO) to start the workflow for invoices without POs and assigned the relevant users. This works fine.

The issue now is how can we enable the workflow to automatically release parked invoices that do have reference to a PO? We tried assigning the workflow user (SAP_WFRT) as the recipient user of the this condition but then the step gets stuck in approval as the SAP_WFRT user does not automatically release parked invoices.