There are two similar use cases for private virtual methods.

1) Abstract private virtual methods
Requires documentation so that it informs the subclasses what the method is expected to do. Se 2) for why declaring them private is useful.

2) Non-abstract private virtual methods
Non-absract private virtual methods are useful for preventing subclasses to call the base implementation directly. The documentation might be useful here to inform potential subclasses what the base implementation does and how they could override that behaviour.

Currently QDoc omits the private members and does not provide any means to expose them in the documentation. While this is sensible for regular methods it is a problem for virtual methods.

I suggest something similar to command \internal just in reverse. What would normally be considered internal and skipped would be exposed.