Finally I’ve solved it.
I set the Looper Provider to “Custom”, the hook to “parent_cat” and left the params empty.
In the themes function.php I put this:
add_filter('cs_looper_custom_parent_cat', function($result, $args) {
$parent_cat_id = isset($args['parent_cat']);
$parent_cat = cs_dynamic_content($parent_cat_id);
$args = array(
'parent' => $parent_cat,
'taxonomy' => 'product_cat',
'hide_empty' => 1,
);
$categories = get_categories($args);
return $categories;
}, 10, 2);
And now the page displays only my top level categories, just as I wanted it.
Best regards
Bengt