xDM

In workflow, is it possible for requester to withdraw the task?? If possible, may I ask about how to set the withdraw?

The workflow can be designed such that the target to whom the next task is transitioned to can reject or cancel the task.  Essentially, the target role can send the task back to the prior originating role where that role can cancel the task rather than forward again.  Or the target role that has the task can cancel the task.