You may have this question on your mind: Can we have a Restockify button on products that can be pre-ordered?
First of all, let us explain what we mean by pre-order products:
When you check the "continue selling when out of stock" box in your Shopify admin, this product can be sold even when the stock is 0, in other words, the product can be pre-ordered. You can see this option on your Shopify admin > Products. By selecting each product and then its variants you'll see it like this:
When this is on, it means your product can be pre-ordered. In this case, you should activate a feature to have the "Notify me" button on these products too. You can find it on your panel> Notify Channels > Advanced > Button Display.
By enabling this feature you can have the "Notify me" on the pre-order products as well.