Xavier,
of course!
I click on 'Product Categories', I can see the categories. So far so good. (0. kep.jpg)
For example, click on "photo wall calendars embroidered table /Hungarian:' Fényképes fali-, asztali-, hímzett naptár'/" in sub-categories: (1. kep.jpg)
"13-sheet calendar" /Hungarian: '13 lapos naptárak'/ (2. kep.jpg)
I click and see: category, URL: subcategory. (3.jpg)
***The (Hungarian) example (Fényképes bögre, korsó, díszkorsó) Photo mug, mug, gift mug and T-shirt and Photo (Fényképes póló) categories are subcategories too, but there is no problem.