Well, if you use something like this:
add_action('admin_menu', 'register_my_custom_submenu_page'); function register_my_custom_submenu_page() { add_submenu_page( 'woocommerce', 'My Custom Submenu Page', 'My Custom Submenu Page', 'manage_options', 'my-custom-submenu-page', 'my_custom_submenu_page_callback' ); } function my_custom_submenu_page_callback() { echo '<h3>My Custom Submenu Page</h3>'; }
Then you will see a submenu in the Woocommerce admin menu. For some reason you cannot do the same with post_type = shop_order.
"shop_order" is the one you should use to place the submenu under "Woocommerce" alone .. but, as I said, I don’t know why it didn’t work with this private post_type.
http://codex.wordpress.org/Function_Reference/add_submenu_page
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