Is there an app to help with Amazon FBA inventory before it sells on amazon?

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We are currently selling our products on Amazon Seller Central, and using Fulfillment By Amazon. However for the consignment inventory that we send to Amazon it is not technically "sold" yet and we cant recognize them as sold. At the moment we are using a new product where we transfer the inventory from our products to a placeholder product, then move inventory out of that placeholder once the products sell on amazon. Is there an easier way to have our consignment inventory tracked other than having a separate placeholder product to store them in as we currently do? It makes things very complicated and we would like to simplify the process.