title: Sorting WooCommerce products by menu_order + popularity
body: <p>I'm trying to make an option to sort WooCommerce products by menu_order + popularity.</p>
  
  <p>So products will be ordered by menu_order, and if they have the same menu_order they will be displayed ordered by popularity</p>
  
  <p>I thought this simple code will work, but it's not:</p>
  
  <pre><code>add_filter('woocommerce_get_catalog_ordering_args', 'add_default_orderby_args');
  
  function add_default_orderby_args($args)
  {
      $orderby_value = isset($_GET['orderby']) ? wc_clean((string) wp_unslash($_GET['orderby'])) : wc_clean(get_query_var('orderby'));
  
      if ('recommended' == $orderby_value) {
          $args['orderby'] = 'menu_order popularity';
          $args['order']   = 'DESC';
      }
  
      return $args;
  }
  </code></pre>
  
  <p>Can it be done?</p>