Qt::WA_DontShowOnScreen permanently disables top-level QWidget visibility

    QWidget* testWidget = new QWidget();
    testWidget->show();
    QPushButton* testButton = new QPushButton(this);
    testButton->setText("Toggle WA_DontShowOnScreen");
    testButton->show();
    connect(testButton, &QPushButton::clicked, this, [testWidget]() {
        static bool toggled = false;
        toggled = !toggled;
        qDebug() << "Set Qt::WA_DontShowOnScreen" << toggled;
        testWidget->setAttribute(Qt::WA_DontShowOnScreen, toggled);
        testWidget->show();
    });