WYSIWYG-Editor produces html syntax instead of wiki syntax when creating headings

When formatting some text as heading, the WYSIWYG editor produces html syntax like:

<h1>heading1</h1>
<h2>heading2</h2>
etc.

Because some macros (like the TOC macro) don't work with that syntax, the editor should rather produce XWiki Syntax like:

1 heading1
1.1 heading2

see the attached video for a detailed demo