function plt_hide_mb_custom_post_type_menus() {
//Hide the "Meta Box" menu.
remove_menu_page('meta-box');
//Hide the "Meta Box → Post Types" menu.
remove_submenu_page('meta-box', 'edit.php?post_type=mb-post-type');
//Hide the "Meta Box → Taxonomies" menu.
remove_submenu_page('meta-box', 'edit.php?post_type=mb-taxonomy');
}
add_action('admin_menu', 'plt_hide_mb_custom_post_type_menus', 11);