\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addPiFlexFormValue('*', 'FILE:EXT:my_ext/Configuration/FlexForms/My.ContentType.xml', 'tx_ext_ContentType');

<T3DataStructure>
    <meta>
        <langDisable>1</langDisable>
    </meta>
    <sheets>
        <sDEF>
            <ROOT>
                <TCEforms>
                    <sheetTitle>LLL:EXT:my_ext/Resources/Private/Language/locallang_be.xlf:ContentType.sheet.options</sheetTitle>
                </TCEforms>
                <type>array</type>
                <el>
                    <optionShowName>
                        <TCEforms>
                        <label>LLL:EXT:my_ext/Resources/Private/Language/locallang_be.xlf:ContentType.option_show_name</label>
                            <config>
                                <type>check</type>
                                <default>1</default>
                            </config>
                        </TCEforms>
                    </optionShowName>
                </el>
            </ROOT>
        </sDEF>
    </sheets>
</T3DataStructure>