I totally agree. Using the barcode area of a product will do the same thing for you though. Then adjusting the packing slip code to show the barcode of a product will work. How many orders per day are you getting? The problem with Shopify is their shipping setup. It is not made for anyone that is shipping more than a few packages a day. If you have under 50 orders per month, Shipstation is only $10 a month and has all of the functionality that you would want and shipping is 10x faster to process.