can we setup default approvers for a particular work item in ibm EWM?

One answer

If you want such capability, you would have to implement a custom follow-up action/participant. Here is an example that I created some years ago: https://rsjazz.wordpress.com/2012/11/30/a-create-approval-work-item-save-participant/ .
I have created custom preconditions/advisors and follow-up actions/participants for customers in service engagements, including automation for approvals. I have rarely seen two customers with matching requirements. That makes it impossible to put something meaningful into the product, it makes more sense to implement custom extensions.