Platform: QTitanRibbon 5.0.1, Qt 5.13.0, VS 2017
But I have same issue in other ribbon, qt and VS release.
in example Application, here are some codes in MainWindow::setCurrentFileName function:
setWindowTitle(tr("%1[*] - %2").arg(shownName).arg(tr("Qtitan Ribbon Office")));
when you run it, whatever you save it or not, the title bar is always have [*] appeared, but it should be removed when saved or setWindowModified(false)；