silverstripe-subsites/src/Extensions/SubsiteMenuExtension.php

<?php

namespace SilverStripe\Subsites\Extensions;

use SilverStripe\Admin\LeftAndMain;
use SilverStripe\Core\Extension;

/**
 * Simple extension to show admins in the menu of subsites.
 * If an admin area should be available to a subsite, you can attach
 * this class to your admin in config. eg:
 *
 * MyAdmin::add_extension('SubsiteMenuExtension');
 *
 * Or you can include the subsiteCMSShowInMenu function in your admin class and have it return true
 *
 * @extends Extension<LeftAndMain>
 */
class SubsiteMenuExtension extends Extension
{
    public function subsiteCMSShowInMenu()
    {
        return true;
    }
}