Category menu with various subcategory level

-- HikaShop version -- : hikashop businessn 2.3.1.
-- Joomla version -- : 3.5x

The problem is in category menu (vertical).
It seems that HikaShop must have a catalog organized with the same level of category-subcategory overall.
I tried also in the demo site.
Here the catalog and the related menu is:

Shoes
◦ Men
◦ Women
◦ Kids
Computing
◦ Peripherals
◦ Computers
E-books
◦ English books
◦ French books
Automobile
◦ Cars
◦ Spare parts
Categorytest1
The Categorytest1 has been created by me (initially without subcategories). A product inside this catagory is not linked in the menu. On the contrary, if I create a Subcategorytest1 under Categorytest1 and if I put inside the product, it will be correctly linked.
Is it an intrinsic limit ?
Thanks for your attention.

Hi,

It depends on the category listing module settings, you can enable the link on the main categories in order to display their products directly.