According to the changelog, a new tab design was added in the latest update. However, this design is different in different places:

And the recipe book still uses the old design:

By the way, would you like to consider adding a license to your project? My friends liked your idea, but they want to improve it and cannot do it, since you have not chosen a license that would allow modification of your work by other people, and Modrinth displays "all rights reserved":

Hello Felix14-v2,
The "Recipe Book" interface will arrive in v1.6.

The license will be updated in a few days.