I am looking for an alternative to pass messages between objects.

You can use custom event,
Define your own events and send them with:
[static] bool QCoreApplication::sendEvent(QObject *receiver, QEvent *event)

Sends event event directly to receiver receiver, using the notify() function. Returns the value that was returned from the event handler.
The event is not deleted when the event has been sent. The normal approach is to create the event on the stack, for example:
QMouseEvent event(QEvent::MouseButtonPress, pos, 0, 0, 0);
QApplication::sendEvent(mainWindow, &event);

@AnneRanch said in Passing messages between objects - alternative to "connect" ?:

Is there a reasonably straight forward way to enable "parent" to access the child form ?

Yes, include the ui_childName.h and in child class add a get method:
UI::ChildName* childUi() { return ui; }
some will say it's bad practice bla bla, it's up to you to decide :)

The other way is to retreive each object by name:
child->findChild<SomeClass*>("objectName")

Of course, the "normal/right way" is to define getters for all the objects you need,
but it is borring I know ;)