Anybody who has run an online store in the past has had to deal with backorders. Just because you don’t have a certain item in stock, that doesn’t mean you can’t keep your customers interested in doing business with you. The WooCommerce Backorder Manager plugin lets you handle backorders professionally.
This plugin lets you quickly see which products are on backorder. You can export them to CSV. The plugin also helps you manage email notifications. The pro version allows you to set a maximum for the number of backorders for products. When that number is reached, the stock status is switched to Out of Stock.
You can find the free version of this plugin here.