Richard here, from the Shopify Guru Team! I hope you're doing well.
At this time we don't yet support scanning barcodes to actually add a product to your inventory through POS, this is something we are looking into and is on the radar of our dev team; expect to see this in the future, but at this time we don't have an approximate timeline.
If there's anything else I can do for you, please don't hesitate to get back in touch! :) You can find me at richard.estabrooks(at)shopify.com
Richard | Shopify