It’s one of the JIT “discoverable” things. When a member is on a Category list page in desktop view it displays in the menu row. That in itself should suggest it’s a menu item.
True, the circle icons may not mean much, especially to a newer member, but there is the down arrow indicating there’s more to be seen. Once that’s opened the fuller descriptions are there.
I confess I didn’t notice it there right away myself. I used my Profile Preference Settings to Watch the categories I had interest in.
But it would be more consistent to have it display more like the topic level setting that is below topics - if there is room for the extra width.