WordPress at a glance
function is not described

_add_post_type_submenus() WP 3.1.0

Add submenus for post types.

This is an internal function for using it by WP core itself. It's not recommended to use this function in your code.

No Hooks.

Return

````. Null. Nothing.

Usage

_add_post_type_submenus();

Changelog

Since 3.1.0 Introduced.

Code of _add_post_type_submenus() WP 5.7

<?php
function _add_post_type_submenus() {
	foreach ( get_post_types( array( 'show_ui' => true ) ) as $ptype ) {
		$ptype_obj = get_post_type_object( $ptype );
		// Sub-menus only.
		if ( ! $ptype_obj->show_in_menu || true === $ptype_obj->show_in_menu ) {
			continue;
		}
		add_submenu_page( $ptype_obj->show_in_menu, $ptype_obj->labels->name, $ptype_obj->labels->all_items, $ptype_obj->cap->edit_posts, "edit.php?post_type=$ptype" );
	}
}