Hi,
If you wanted to search for process instance, you can make it a custom measure.
I believe process variable P_document is the WI instance ID, be careful for AND split - there can be multiple P_documents per process instance.
You have WI instance id, you want to call process report API with filter p_document = wi instance id.
Somewhat similar use case here, might be some help - not exactly.
Overall, it will be somewhat complex, consider if it is really necessary.
Best regards,
Taka