Add admin page to the top of the admin panel

Try this code:

add_action('admin_bar_menu', 'wp_toolbar_custom_menu', 100);
function wp_toolbar_custom_menu($admin_bar){
    $admin_bar->add_menu( array(
        'id'    => 'menu-item',
        'title' => 'Menu Item',
        'href'  => '#',
        'meta'  => array(
            'title' => __('Menu Item'),            
        ),
    ));
}