<script src="//cdn.ckeditor.com/4.16.1/standard/ckeditor.js"></script>
<script>
  $(() => {
    if (CKEDITOR.instances) {
      for (let name in CKEDITOR.instances) {
        let instance = CKEDITOR.instances[name];
        // 個々のconfigが弄れる
      }
    }
  });
</script>