@xumuk As said earlier it is a limitation. But if you still need it you should have a look at the 2nd and 3rd paragraph in the link which I posted earlier. Basically you will have to do this:

QQuickWidget *wd = new QQuickWidget(this); wd->setAttribute(Qt::WA_AlwaysStackOnTop); wd->setClearColor(Qt::transparent); //and the opacity can be set in QML istelf for eg. for a Rectangle Rectangle { width: 300 height: 300 color: "green" opacity: 0.5 }

If you load this QML in the QQuickWIdget and put a QWidget in background it should be visible.