Resume BPA Workflow from a specific step using API

[gabpetro]

Hi all, 

I am developing a workflow on SAP BPA that requires the user to perform activities via webGUI transactions on an SAP S4 HANA private cloud. The link within the task form opens a web GUI. Once the activity on the ERP is completed, how can I resume the workflow from that specific step?

I have thought of two possible solutions:

1. Create a form on the task and then call an OData service that performs the operation on the system via BAPI or other means, thus eliminating the need to open the web GUI.
2. Modify the program/transaction to call the workflow API at the point where it was interrupted. But which API should I use? In the API reference https://api.sap.com/api/SPA_Workflow_Runtime/path/patch_v1_workflow_instances__workflowInstanceId_, I couldn’t find anything that allows me to resume a specific workflow from a specific step.

Thank you all.