Hi,
You have two solutions:
- You install Advanced Modules Manager Pro.
It will add advanced restrictions to your modules, including a setting to restrict the display of the module per category of HikaShop.
- Instead of adding the module to a position, you could add the module in the description of the category with the "loadmodule" plugin of Joomla:
www.joomlashack.com/blog/joomla/loadposition-loadmodule/
Then, make sure that the "show description" setting of your hidden products listing menu item is activated so that it will display the description of the category at the top of the products listing, which will include the module for that specific category.