Is it programmatically possible to forward an open WorkItem to a new owner?
The intention is to automatically forward all open WorkItems to the manager when an identity leaves the company. It seems that changing the owner directly on the WorkItem object does not take effect.
Create a new rule of this type and write your logic. Refer the below screenshot.
Here, I have written a simple logic to return spadmin in all cases but in your case, write your logic based on your requirements. Make sure you return the identityName of the new user where you want to forward the work item.