Hi,
The "waitlist" could be activated and configured in the backend.
www.hikashop.com/en/support/documentatio...-config.html#display
Activate waitlist feature : That option will add an "Add me to the wait list" button on your products page when the products are out of stock so that users can be notified when the products stock is replenished (when you set a quantity for the products).
You can also add that button on a per product basis.
That means that you will have to choose to display or not the button for each product (you will then find that option when you edit your product).
Please note that you will also have to publish the HikaShop Product Wait List Notification plugin via the Plugins tab and configure your CRON task via the CRON tab of the configuration page.
This option is available in all commercial versions of HikaShop.
So when a product as no stock (so when the product quantity is 0), the waitlist button would be displayed in the product page.
The "waitlist" plugin will check the quantity of products and when some the stock will allow it, some emails would be send to customers.
Regards,