Unable to edit requisition which has been approved and an purchase order has been created (SSP)

Summary:

a) Purchase Order created using requisition using SSP.

b) Would like to add a new line at the requisition level not at the Purchase Order (Change Order).
c) Since the client does not want to give the PO related roles to the employees.

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):