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.

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_themes_utility_last();

Changelog

Since 3.0.0 Introduced.

Code of _add_themes_utility_last() WP 5.7.1

<?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' );
}