Here are steps for adjusting custom workflow templates. In this document, Purchase Order Approval is an example.
1. Test the Fiori app with the standard workflow template. WS20000075.
If you use custom workflow template, make sure the Fiori app works fine. To validate this, temporarily activate the standard workflow template and test the app.
Workflow Template WS20000075
Activate the triggering event
Update the entry in the task ID customizing table. Add or change the approval task ID TS20000166.
When a PO is created, a workflow instance is created based on the standard workflow template. Make sure the Fiori app works fine.
2. Test the Fiori app with your custom workflow template.
Deactivate the triggering events.
Make sure the approval task ID is maintained if you use custom approval task. App Implementation: Approve Purchase Orders – SAP Fiori Apps – SAP Library
When a PO is created, a workflow instance is created based on your custom workflow template.
Test which function does not work.
3. Compare the workflow templates and the approval task container.
Compare the standard template and your custom template.
Please note that workflow template level difference is not important because Fiori apps only handle workitem level.
Check the approval step and the container binding.
If some of container binding is different from the standard task in your custom task, add the missing container elements.
4. Test the Fiori app with your custom workflow template after adjusting the container elements.
You should create a new PO for starting a new workflow instance.
5. Set external breakpoints and find the root cause.
If the app does not work even after adjusting the container elements. Setting external break points is a quick way to find a root cause.
Method: GET_LIST, GET_PO_HEADER_DETAILS_WITH_X, GET_PO_ITEMS_DETAILS_WITH_X, SET_DECISION
6. Find out reasons why the custom workflow template was created
I guess that most of the custom workflow templates were created many many years ago. Probably those initial requirements are not valid any more and current requirements can be covered by the standard workflow template. In that case, use the standard workflow template or copy the standard workflow template and migrate the required changes. The point is keeping the same workflow container elements from the standard.
7. The last option is Fiori My Inbox
If your custom workflow template is completely different from the standard and there is no way to adjust, you can use Fiori My Inbox.