Possibility to set default Open Graph tags for categories

Hi,

There is indeed no code in HikaShop to have open graph tags on listings. They are only for the product pages.
Normally, open graph tags are meant to describe content pages, not listings.
If you look at their website ogp.me/ the type tag only has content elements like article, book or movie. Not classification elements like "category" or "group".
So I'm not sure it would make much sense to add open graph tags there.
If you need to, you can edit the file "listing" of the view "product" via the menu Display>Views and you can add the tags to the header with custom PHP code.