Hi @alban,
This isn't something we offer as a functionality, rather a "home-made" alternative using Prismic. The solution Alexandre offered in his post described the steps we took, and you can reproduce that on your own project if you'd like.
Tabs can be used in Custom Types to organize your fields. You can create them in any Page/Custom Type in your Slice Machine here:
They'll give you the chance to for example add fields in the static zone: this is where you'd put the content relationship Alexandre mentioned. It will keep this A/B testing tool off the Main page where your content is and give your Custom Type some structure. You can create as many as you'd like, and organize it however you wish, it won't impact the structure of the API response. If you'd like to know more, you can check out this post:
Because this is just one way to do it, there's no documentation on our version of A/B testing aside from the growthbook one shared above, but if you try it yourself and you have questions, feel free to ask them on the forum and we can take a look 