A customer places an order, they don't receive the item, you need to send it again. So you want to clone the sales order  so you can resend it ( with zero price) .  or you want ot edit the sales order to add another item, and then create a new invoice. This is important because Amazon addresses are not saved in the same way as other customers so starting a whole new order for the person is very daffy as you have to go onto amazon and find their address etc.