如果您可以控制wp_nav_menu() 调用，可以实现自定义Walker_Nav_Menu class 用于对将导航菜单项数组呈现为HTML进行细粒度控制。

如果要添加的项目的标记与默认值相同Walker_Nav_menu 已生成，您可以使用\'wp_get_nav_menu_items\' filter 钩住以添加；虚拟导航菜单项；在将对象处理为HTML之前，将其添加到数组中：

/**
 * Add a login/logout link to the nav menu in the `primary` location, as a child
 * of a menu item for a Page with the slug `members` (if present).
 *
 * @see https://wordpress.stackexchange.com/a/390893/25324
 *
 * @param WP_Post[] $items The WP_Post objects representing menu items in this menu.
 * @param WP_Term   $menu The WP_Term object representing this menu.
 * @param array     $args The arguments used to retrieve menu items associated with this menu.
 * @return array The filtered $items array.
 */
function wpse390890_insert_primary_nav_login_link( $items, $menu, $args ) {
  if( is_admin() )
    return $items;

  // Bail out if this menu isn\'t `primary` or `primary` is being loaded in the dashboard.
  if( $menu->slug !== \'primary\' || is_admin() )
    return $items;
  
  // Find the ID of the Page with the slug `members` in the menu items.
  foreach( $items as $item ) {
    if( $item->post_type !== \'page\' || $item->post_name !== \'members\' )
      continue;
    
    $members_page_id = $item->ID;
    break;
  }

  // Bail if the `members` page is not in this menu.
  if( ! isset( $members_page_id ) )
    return $items;
  
  $logged_in  = is_user_logged_in();
  $link_title = __( $logged_in ? \'Log In\' : \'Log Out\', \'wpse390890\' );
  
  // Insert a new WP_Post object for the link.
  $items[] = new WP_Post(
    (object) [
      \'ID\'               => \'user-login\',
      \'menu_item_parent\' => $members_page_id,
      \'classes\'          => [ \'member-auth-link\' ],
      \'type\'             => \'virtual\',
      \'object\'           => \'virtual\',
      \'title\'            => $link_title,
      \'attr_title\'       => $link_title,
      \'url\'              => $logged_in ? wp_logout_url() : wp_login_url(),
    ]
  );
  
  return $items;
}

add_filter( \'wp_get_nav_menu_items\', \'wpse390890_insert_primary_nav_login_link\', 10, 3 );

看见wp_setup_nav_menu_item()\'s implementation 有关要指定哪些字段以及如何指定的提示WP_Post 对象将转换为表示导航菜单项的对象。var_dump()ing公司$items 在上面的过滤器中，也是探索菜单中已有项目的格式和属性的好方法。