function plt_hide_visitors_app_menus() {
//Hide the "Visitors" menu.
remove_menu_page('visitors-app/admin/start.php');
//Hide the "Visitors → Start" menu.
remove_submenu_page('visitors-app/admin/start.php', 'visitors-app/admin/start.php');
//Hide the "Visitors → About" menu.
remove_submenu_page('visitors-app/admin/start.php', 'visitors-app/admin/about.php');
}
add_action('admin_menu', 'plt_hide_visitors_app_menus', 11);