HelloWorldModuleMenu2.php

<?php
class MyModule extends Tendoo_Module // should alway extends Tendoo module
{
    public function __construct()
    {
        parent::__construct();
        $this->events->add_filter( 'admin_menus', [ $this, 'menus' ]);
    }
    
    /**
     * register Menu
     * @param array menu
     * @return array 
    **/
    public function menus( $menus )
    {
        // menu should have a namespace
        $menus[ 'mymenu' ]  = [
            [ // fisrt menu definition
              'title'   =>  __( 'Custom Menu' ),
              'disable' => true, // this will won't be displayed as a child menu.
              'href'    =>  '#', // it can be something else using site_url(),
              // 'permission'  =>  [ 'custom.permision' ], // optional to hide the menu if the use doesn't have the required permission. 
                                                        //You should comment this section if the permission has not yet been created
              'icon'    =>  'fa fa-home', // font awesome icon are supported
            ], [ // second menu definition
              'title'   =>  __( 'Sub Menu' ),
              'href'    =>  '#',
              'icon'    =>  'fa fa-home', // icon aren't supported for sub menu
            ], [ // second menu definition
              'title'   =>  __( 'Sub Menu 2' ),
              'href'    =>  '#',
              'icon'    =>  'fa fa-home', // icon aren't supported for sub menu
            ], 
        ];
        
        return $menus
    }
}