wordpress admin – create a page without it appearing in the side menu

Set the parent_slug property to null, example;

add_submenu_page( 
           null,            // -> Set to null - will hide menu link
          'Page Title',    // -> Page Title
          'Menu Title',    // -> Title that would otherwise appear in the menu
          'administrator', // -> Capability level
          'menu_handle',   // -> Still accessible via admin.php?page=menu_handle
          'page_callback' // -> To render the page
    );

This will hide the sub menu page from your parent (top level) menu link.

That’s it. If you have any query then comment here.