Cs-cart：如何通过2个参数同时组织产品分类？

I need to sort products in category by 2 parameters, for example, by availability in stock (~amount) and by price, in order to display not-in-stock products on last pages, but sort all by price simultaneously. How to do it?

It is not possible to make it via an add-on, but you can do it by modifying the app/functions/fn.catalog.php file.

Find this function: fn_get_products There is "sorting" code:

$sorting = db_sort($params, $sortings);

The sorting variable after processing looks like

ORDER BY products.price DESC

You can extend it by your code. For example:

if (!empty($sorting)) {
    $sorting .= ', my_field ASC';
}

You will get something like this

ORDER BY products.price DESC, my_field ASC