Any option to auto Approve/Reject a PO in My Inbox in sap Public cloud based on a custom field value

[Gahan_Narayan]

We have created a Purchase Order (PO) approval workflow using SAP Build Process Automation (SBPA) to handle all validations and approvals. However, in the final step, we encountered a limitation: the API does not allow us to directly change the PO status to “Approved” or “Rejected” and release the PO since 'PurchasingProcessingStatus' is a read only field and also referred to this post: whether-the-purchase-order-can-be-approved-through-the-api

To work around this, we are using the Flexible Workflow in S/4HANA Public Cloud. The PO remains in “In Approval” status until the SBPA process is complete. Once all approvals in SBPA are done, we send a PATCH call to update a custom field in the PO.

In the Flexible Workflow, we’ve implemented a BADI : SWF_CHECK_ACTION_ALLOWED that checks the value of this custom field when the user click on any action from My Inbox. If the field shows that the SBPA process is complete, we allow the user to approve the PO in S/4HANA.

Now, we want to further improve this by automating the approval in S/4HANA without requiring manual user action.

Our question:
Is there a way to automatically approve the PO in the Flexible Workflow/ My Inbox once the custom field is updated from SBPA?

or

Can we use any BADI or other method/Jobs to approve the PO in My Inbox in S4 public cloud, without requiring a user to log in and manually approve it in S/4HANA? or is there a possibility to use a certain CDS with behavior definition exposed as an API allowing to change the status of the PO which is read only currently in the API: PURCHASEORDER_0001 API 

Thank you in Advance.

SAP S/4HANA Cloud Public Edition 

[OwenLiu]

Removed general tag.