You must be talking about this?
Let me know if doesn't help.
Thanks & Regards
If you add a custom meta field to the lineitem it will be visible in the cart viewing in commerce under the line items section.
How to view custom metadata added to line item? It is visible until the status of line item is completed. The new property was added from GUI as explained in http://jondjones.com/learn-episerver-cms/episerver-commerce/adding-custom-metadata-to-the-lineitem-class-in-episerver-commerce-via-code.