TYPO3 Core

Let's imagine a model with the name quiz. This quiz has an inline field questions, which collects items of the model quizquestion. TCA definition example:

        'questions' => [
            'label' => '',
            'config' => [
                'type' => 'inline',
                'foreign_table' => 'domain_model_quizquestion',
                'foreign_field' => 'quiz',
                'foreign_sortby' => 'sorting',
                'maxitems' => 9999,
                'appearance' => [
                    'collapseAll' => 0,
                    'levelLinksPosition' => 'top',
                    'showSynchronizationLink' => 1,
                    'showPossibleLocalizationRecords' => 1,
                    'useSortable' => 1,
                    'showAllLocalizationLink' => 1
                ],
            ],
        ],

Now the model quizquestion has a flexform field answers :

        'answers' => [
            'label' => '',
            'config' => [
                'type' => 'flex',
                'ds' => [
                    'default' => 'FILE:EXT:ext/Configuration/FlexForms/Answers.xml',
                ],
            ],
        ],

The flexform has sections:

<T3DataStructure>
    <sheets>
        <sDEF>
            <ROOT>
                <type>array</type>
                <el>
                    <answers>
                        <type>array</type>
                        <section>1</section>
                        <el>
                            <answer>
                                <type>array</type>
                                <title>Antwort</title>
                                <el>
                                    <text>
                                        <label>Text</label>
                                        <config>
                                            <type>string</type>
                                        </config>
                                    </text>
                                    <correct>
                                        <label>Ist korrekt?</label>
                                        <config>
                                            <type>check</type>
                                            <renderType>checkboxToggle</renderType>
                                        </config>
                                    </correct>
                                </el>
                            </answer>
                        </el>
                    </answers>
                </el>
            </ROOT>
        </sDEF>
    </sheets>
</T3DataStructure>

This just won't work in the typo3 form backend. The sad result of this config: