Laura,
since the chapter numbers are indeed generated automatically by DNG in the context of a module to display the hierarchy of Headings they are not part of the Heading artifacts, thus cannot be referenced when linked.
To sort of achieve what you might try I suggest creating link types "refers / referred to" or use the "link to" and "link from" linked types, show the link types explicitely in the view of a module and instead of putting the reference in the text of the requirement, explicitely "refer to" link the requirement to the respective chapters (of type Heading). They will show with their artifact id::chapter title, but at least that will reflect the actual chapter artifact, always up to date and easy to look at via hover-over or by clicking.
Since to achieve exactly what you are looking for is not possible today as far as I know I suggest opening an enhancement request on jazz.net against DNG if this approach is not sufficient.


If this makes sense and helps you please mark the answer as accepted.

- Arne