Hi,
In each menu item, via the Joomla menu manager, under the "products options" tab, you'll find thumbnails size settings for the listings of that menu item.
So if you have different menu items for different categories, you can have different thumbnail sizes for different categories.
So you have two ways to go about it:
- you can reproduce the category tree you have in HikaShop in the menu manager with one menu item per category with the corresponding parent elements, etc. That way, when you browse the categories on the frontend, the system will switch the menu items automatically based on the attached main category.
- You can create a menu item specific to a category, configure that menu item to display with thumbnails of a different size, get the URL of that menu item, set that URL in the "canonical URL" field of the category, and activate the "force canonical URL on listings" setting of the HikaShop configuration.