how to create custom plugin submenu in wordpress?

 how to create custom plugin  submenu in wordpress?

make new folder in plugin after whatever you want your folder name, remember that file name and folder name same .

make folder in this folder wp-content/plugins/
exmaple : wp-content/plugins/viral/viral.php
viral is your plugin folder and viral.php is your plugin file
now add code in viral.php file.

viral.php

<?php
/**
 * @package viral
 */
/*
plugin Name: vira-plugin
plugin URI: https://vdcodin.blogspot.com/
Description: this is my custom plugin made by your name other wise details about plugin
Version: 4.1.7
Author: viral
Author URI: https://vdcodin.blogspot.com/
License: GPLv2 or later
text Domain: viral
*/
add_action('admin_menu','viral_menu');
function viral_menu(){
    add_menu_page(
        'viral', // page title
        'viral', // menu title
        'manage_options', // by-default admin site
        'dashboard', // this is called page slug
        'my_function',// callback function which we called
        'dashicons-dashboard', // this is our icon
        6      //  this is our plugin position 
    );
    //we have only one sub menu then why its showing 2?
    //lets make this one
    add_submenu_page(
        'dashboard', // parent slug beause we need submenu of this menu
        'first submenu', // page title
        'first submenu', // menu title
        'manage_options', // by-default admin site
        'dashboard', // menu slug
        'my_function' //call function which we click on sub menu and open that page      
    );
    add_submenu_page(
        'dashboard', // parent slug beause we need submenu of this menu
        'second submenu', // page title
        'second submenu', // menu title
        'manage_options', // by-default admin site
        'second-submenu', // menu slug
        'second_submenu' //call function which we click on sub menu and open that page      
    );  
    add_submenu_page(
        'dashboard', // parent slug beause we need submenu of this menu
        'third submenu', // page title
        'third submenu', // menu title
        'manage_options', // by-default admin site
        'third-submenu', // menu slug
        'third_submenu' //call function which we click on sub menu and open that page      
    );  
}

if you still confused watch my video:

link : https://youtu.be/wcWrQRlJhnc