Method to conceal (hide but stay buyable) a product without code changes in theme/templates?

[GreenDudu]

Is there any method to conceal a specific product (either by settings or programmatically via API) from showing up in a store, but stay buyable (it gets added programmatically to the cart/checkout)?

We want to do basically do the same like described in this post, and we were able to hide it for SEO, however all methods we see to completely conceal it, depends on code changes in the theme.

We've checked if there is an option to use Collections for this, but no success.

We can not work with code changes (in the theme), as this is a public app so depending on custom code changes is a support nightmare.

Is there any Shopify App that does this or something similar? How do they do it?

We want do do this for a better UX but also as it is a mandatory request we've got out of the submission process.