WordPress at a glance
function is not described

_add_themes_utility_last() WP 3.0.0

Adds the (theme) 'Editor' link to the bottom of the Appearance menu.

No Hooks.

Return

Nothing (null).

Usage

_add_themes_utility_last();

Code of add themes utility last: wp-admin/menu.php WP 5.2.2

<?php
function _add_themes_utility_last() {
	// Must use API on the admin_menu hook, direct modification is only possible on/before the _admin_menu hook
	add_submenu_page( 'themes.php', __( 'Theme Editor' ), __( 'Theme Editor' ), 'edit_themes', 'theme-editor.php' );
}