How to put data into custom fields

Hi,

I'm not following you.
How did you create a custom field that isn't in the hikashop_product table ?
Or maybe you mean that it's not an actual "hikashop custom product field", but an input that you added to the products and which is saved somewhere else, not related to the custom fields system of HikaShop ?

In any case, if you want to load data from another table for each products on a listing, the simplest is to have a query for each product in your view file override (listing_img_title by default) basing yourself on $this->row->product_id
You sure could add a join on the products loading query, but it's more complex than just overriding the view file and adding a query there.

The product data is not stored in the session.
You would have to query the DB everywhere where you want to use it.