Hi there @dani_bazzaal,
Thanks for sharing with the Community!
Unfortunately, you cannot manually add someone to the back in stock flow. The only way a customer can trigger the flow is to subscribe on your website. With that being said, this is an open feature request that I can add your information and feedback to, but I won't have an ETA on when this may be developed at present.
However, there is a workaround to manually add the users into the Back in Stock flow which requires the use of the Back in Stock API. Essentially what you'll do is send all of the users and the items they subscribed to through the API. It's a bit technical so I recommend working with a hired developer, if needed. Everything that you need to execute this is provided in our Back in Stock for Developers guide.
Hope that helped,
Alex
Hi Alex!
Thank you so much for your reply, will try to work on this with a developer.