I used it that way, it the example does not work, too, in my case.

'CPDAttributes' => [
'type' => 'list',
'label' => 'Attribute Mapping',

                'items' => [
                    'qcode' => [
                        'type' => 'select',
                        'label' => 'QCode',
                        'options' =>
                            $this->createList('qid', $event->get('survey')),
                        'current' => $this->get('qcode[', 'Survey', $event->get('survey')) // todo is this a LS bug "["
                    ],
                    'pdField' => [
                        'type' => 'select',
                        'label' => 'CPD Attribut',
                        'options' => $this->createList('cpd', $this->id),
                        'current' => $this->get('cpdField[', 'Survey', $event->get('survey'))
                    ],
                ],
            ],