I created a qch file using the qhelpgenerator (5.4.1) from an output of doxygen. (I used the doxygen settings to automatically generate the qch).

I can "Add..." the qch file under Tools->Options->Help->Documentation and after Apply / OK I can use the help in Content and Index Search.
Everything looks good.

But when I stop QtCreator and restart it the added help is not in the Documentation Listing anymore and the content or index search does not show up any of the formerly added help.