How to add a new line to a Purchase Order created via Requisition from old UI in RSSP (24D)

Summary:
How to create a requisition backed Change order in the RSSP UI . On clicking Edit against the Requisition for which PO was already created , the system asks to enter the description & a change order is created which shows the existing lines .

However , how do we add a new line to this change order

Content (please ensure you mask any confidential information):

How to create a requisition backed Change order in the RSSP UI . On clicking Edit against the Requisition for which PO was already created , the system asks to enter the description & a change order is created which shows the existing lines .