main.py

def portal_purchase_order_details(self, c_id, upload=None, **kw):
  ...
  ...
  ...
  order.write(po_values)
  order.save_quoted_lines()
  if upload:

purchase.py

class PurchaseOrder():
    _inherit = "purchase.order"
    ...
    ...
    def save_quoted_lines(self):
        for line in self.order_line:
            line_data = line.copy_data()
            self.env['purchase.quoted.line'].create(line_data)