A few hundred of headings I want to make clickable to chapters
and back. This (unusual in such a book) possibility of reverting to the ToC is intended to serve a comprehensive understanding of the chapters. Anyway, further explanations why this seems necessary would go too far.
The manual (boring) way to insert id's I know: I look for the
smart way.
To insert fix id's with S&R to headings leads to Check book/
Error: Dublicate id:
The id xyz is present on more than one element in Inhalt.html. This is not allowed.