Park and Retrieve is a feature that allows a transaction to be hold, so that customers can place an order in advance, and add more orders later, then pay for the bill when they're done.
Here is a simple illustration on how you can use Park and Retrieve in retail store.
I. Park order through selling pages
Step 1. Select "PARK" button and fill with the customer name or identification sign
Step 1. To pull back the order just now, you can click the "RETRIEVE" button and choose which order you want to callback
Step 2. After you click RETRIEVE, you can click Pay button to complete the transaction
Note: If the customer wants to add new item/product, you just adding the item and click Pay if the customer wants to pay the items.