I created a custom post type with taxonomy and now want to allow users (of a specific user group) to post only one single post in a specific category.

If the user has already posted a post, he can only edit his own post (I already have the PHP for that).

I found a lot of solutions that users can only post in a specific category or only edit their own posts, but no-where an conditional that the user can only post one post.

The functionality might be seen as a “second profile”, it should be like a profile (Users can post one post, edit this post, all users and guests can view the post).

I would have several ideas, maybe a conditional, if the user has 0 posts in the category, than he has the right to post?