ty very much for you reply.
I have to change my question then.
I’m trying to make a new admin menu voice.
Very much like piklist about/welcome page.

I start by adding in my plugin php:

add_filter('piklist_admin_pages', 'my_custom_admin_pages');
  function my_custom_admin_pages($pages) 
  {
    $pages[] = array(
      'page_title' => __('Page title')
      ,'menu_title' => __('Menu title')
      ,'capability' => 'manage_options'
      ,'menu_slug' => 'mycustomadminpages'
      ,'menu_icon' => MY_PLUGIN_URL.'imgs/my-icon.png'
      ,'page_icon' => MY_PLUGIN_URL.'imgs/my-icon.png'
      ,'single_line' => true
      ,'default_tab' => 'Basic'
    );
  
    return $pages;
  }

that correctly create the ‘Menu title’ menu button (with correct icon)
I miss how to specify that /parts/admin-pages/mycustompage.php will be the target of ‘Menu title’ menu button link.
Currently it displays a blank page with ‘Page title’

Sorry for the silly question but I think that could integrate your documentation page
Documentation: Settings / Admin Page Parameters

yes i know. never understimate the stupidity of some of yours readers.