add_action('parse_query', 'devise_product_attribute_sorting_query_2');
function devise_product_attribute_sorting_query_2( $query ) {
    global $pagenow;
    $taxonomy  = 'pa_design';
    $q_vars    = &$query->query_vars;
    if ( $pagenow == 'edit.php' && isset($q_vars['post_type']) && $q_vars['post_type'] == 'product' && isset($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;
    }
}

function devise_filter_design_form() {
    $selected = isset($_GET['pa_design']) ? $_GET['pa_design'] : '';
    wp_dropdown_categories( array(
        'taxonomy'         => 'pa_design',
        'name'             => 'pa_design',
        'show_option_none' => 'Фильтр по цвету',
        'show_count'       => false,
        'hide_empty'       => true,
        'selected'         => $selected
        )
    );
}
add_action( 'restrict_manage_posts', 'devise_filter_design_form', 25 );