Primary category

I think it’s a general problem of WP. But maybe you know a solution:

If you define several categories for one post, the alphabetically first one is always displayed. With plugins you can set primary categories, but this has no effect on the display. The plugins only include the primary category in the permalink. I searched for three hours and tried plugins – without success. I have not found a solution.

Is there any solution?

The page I need help with: [log in to see the link]