Unfortunately you can't combine your saved orders. You'll have to delete your saved orders and create a new order which includes all of the items you'd like to sell.
If you're creating a particularly large order, why not check out our iOS and Android apps? You can save yourself some time by scanning your items directly from your phone!
Please note that our pricing algorithms dictate the item's price once it has been scanned into the valuation engine. If you happen to scan an item's barcode across multiple saved orders, the item(s) in question can be valued differently.