A common transaction here in the brick and mortar store is selling a musical instrument, and taking a customer's old instrument in on trade towards the price of the new instrument. How would I go about ringing that up in Shopify POS?
One feature we like is that ability to name a discount. In this case I'd discount the item and call it "trade in" or something. Then I presume you'd add the acquired instrument into inventory manually after the transaction if you plan to re-sell it.