Great question, @MMWTCtreasurer - this is definitely doable. 

Once items are added to a sale using the Point of Sale mobile app, there should be an available icon at the top of the Checkout tab labeled Current Sale. This icon will have a number next to it, indicating how many items are currently attached to the sale.

Once you've added all items to sale, simply click on the Current Sale icon. This will give you a full list of items in the sale that can be edited from this page.

I hope this information is helpful! Don't hesitate to reach out with any additional questions.