How to add product display nid to user order view?
You can use the module commerce_product_attributes to show more product details on the line item.


  Attribute field for line item: This field allows the presentation of
  the product in the shopping cart by a separated view mode. A new
  product display is added. There you can define the fields which should
  be displayed for this product type in the shopping cart.


While it can be used on the shopping cart, it can also be used on the Orders view.