fluid - typo3 flexform html content element add in extension -

how can add html content element in flexform in typo3. have tried

<settings.sdef1.sociallinks>                                         <tceforms>                                             <exclude>1</exclude>                                             <label>social links</label>                                             <config>                                                 <type>text</type>                                                 <rendertype>t3editor</rendertype>                                                 <format>html</format>                                                 <cols>30</cols>                                                 <rows>5</rows>                                             </config>                                         </tceforms>                     </settings.sdef1.sociallinks>  

which not working.

ref : https://docs.typo3.org/typo3cms/tcareference/reference/columns/text/index.html#rendertype