WP-create-admin-page.php

<?php

add_action('admin_menu', function () {
    $parent_slug = 'edit.php?post_type=page'; // "Pages"
    $page_title = 'My Plugin Submenu Page';
    $menu_title = 'My Plugin Submenu Page';
    $capability = 'edit_pages';
    $menu_slug  = 'myplugin-submenu-page';
    $page = 'myplugin_submenu_page';
    add_submenu_page( $parent_slug, $page_title, $menu_title, $capability, $menu_slug, $page);
});
function myplugin_submenu_page(){
    echo "<h1>Sub menu page content goes here.</h1>";
}

// global $menu, $submenu;
// echo "<pre>MENU: \n".print_r($menu,true)."</pre>";
// echo "<pre>SUB-MENU: \n".print_r($submenu,true)."</pre>";
// die;

// TO MODIFY INSTEAD:
add_action( 'admin_menu', function () {
    global $menu, $submenu;
    foreach ($menu as $menuKey => $menuItem)
        if ($menuItem[0] == 'Products')
            $menu[$menuKey][2] = 'https://google.com/'; // wtv link you want

    // UPDATE:
    // remove the sub menu as well (note the GLOBAL var define above)
    $submenu['edit.php?post_type=product'] = ''; 
    unset($submenu['edit.php?post_type=product']);
});