EmailTemplatesListPanel.inc.php

<?php
namespace APP\components\listPanels;
use \PKP\components\listPanels\PKPEmailTemplatesListPanel;
 
class EmailTemplatesListPanel extends PKPEmailTemplatesListPanel {
   public function getConfig() {
      $config = parent::getConfig();
      $config['filters'][count($config['filters']) - 2]['filters'][] = [
         'param' => 'toRoleIds',
         'title' => __('default.groups.name.subscriptionManager'),
         'value' => ROLE_ID_SUBSCRIPTION_MANAGER,
      ];
      return $config;
   }
}