From the RFI or Submittals log, navigate to the details page.
If the item has not been forwarded or responded to there will be a delete button.
Click delete to remove the submittal from this project.
If the submittal should be in a different project, you can use the Log New Incoming Submittal button in that project to enter it there.
What if there is no Delete button?
If the RFI or Submittal was sent out-of-house then your organization must have a record of it because a 3rd party is now involved. For that reason, the Delete button is not available if the item has been forwarded or returned.