Important: Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct
Why registerUserData of QObject is undocumented?
I found many examples of using userData mechanism on different forums, but officially it is undocumented - why?
Because it's internal and thus not part of the public API
why it has public declarations, besides almost of qt framework uses pimpl idiom - why userData not pimpl protected?
Our department under my direction posts tons of bugs into qt bugtracker -
whole qt disign sucks - ...that's why.... so..another approvement
That I don't know, to answer that question you should rather post on the interest mailing list. This forum is more user oriented.
Based on the name of the class, I'd say that Qt's dynamic properties would be the right way to go.
I know, I know, sorry for critic, but qt have really many strange solutions.