How to Cancel/Delete the Workflow Notification

Navigate to Status Monitor-->Query for the transaction-->Click the Activity History-->Click on cancel workflow.

Run the hr_transaction_api.rollback_transaction( p_transaction_id => sshr_transaction_id ,p_validate
=> false );  to remove the record, so the same is not shown as pending in the notification page.

if above didnt remove then run the concurreng program available in System Administrator or Workflow Administrator

Purge Obsolete Workflow Runtime Data

Parameters: Item Type --> HR

                    item Key --> <pass_item_key>

And the notification will deleted.