How can I add "filter by brands" filter function in the backend?

Hello there.. Please replace this action:
add_action('parse_query', 'product_tags_sorting_query');

With this filter and it should work:
add_filter( 'parse_query', 'product_tags_sorting_query' );

Brgds
Rune

Well as from what i can see in your code you are still using “add_action” which needs to be replaced with “add_filter”.

Give this code a trie, it is tested and works:

// Filter products by brand in WP Admin

add_action( 'restrict_manage_posts', 'aws_brand_products_sorting' );
function aws_brand_products_sorting() {
    global $typenow;
    $post_type = 'product'; // change to your post type
    $taxonomy  = 'pa_brand'; // change to your taxonomy
    if ($typenow == $post_type) {
        $selected      = isset($_GET[$taxonomy]) ? $_GET[$taxonomy] : '';
        $info_taxonomy = get_taxonomy($taxonomy);
        //$selected      = isset($_GET[$info_taxonomy->name]) ? $_GET[$info_taxonomy->name] : '';
        wp_dropdown_categories(array(
            'show_option_all' => __("Show all {$info_taxonomy->label}", "aws-multi-functions"),
            'taxonomy'        => $taxonomy,
            'name'            => $taxonomy,
            'orderby'         => 'name',
            'selected'        => $selected,
            'show_count'      => true,
            'hide_empty'      => true,
        ));
    };
}
add_filter( 'parse_query', 'aws_brand_products_sorting_query' );
function aws_brand_products_sorting_query( $query ) {
    global $pagenow;
    $post_type = 'product'; // change to your post type
    $taxonomy  = 'pa_brand'; // change to your taxonomy
    $q_vars    = &$query->query_vars;
    if ( $pagenow == 'edit.php' && isset($q_vars['post_type']) && $q_vars['post_type'] == $post_type && isset($q_vars[$taxonomy]) && is_numeric($q_vars[$taxonomy]) && $q_vars[$taxonomy] != 0 ) {
        $term = get_term_by('id', $q_vars[$taxonomy], $taxonomy);
        $q_vars[$taxonomy] = $term->slug;
    }
}

Brgds
Rune

Hi again,

Yes i have developed wordpress/woocommerce plugins for 15 years but had the brake on for the last 2 years as i have been a little tired of developing. But just send me an email at: rune@arctic-fritid.no and we will see if i can be of any help.

Brgds
Rune