Add a class for the product listing page only

Hi,

If you want to add extra classes to the "body" element of the page, you'll need to edit your template files. I can't say exactly how that should be done since different templates structure are different.
With the default template of Joomla, on Joomla 4, I do see different classes there though:
i.imgur.com/Cdvaokc.png
i.imgur.com/ZdGxcz1.png
So you could use .com_hikashop.view-product.task-show for the product details page and .com_hikashop.view-product.task-listing for the listings. So if your template is done properly, following what the default template does, you should see these classes.
And if not, I can only recommend you to check with your template provider.