How to get element inside QWindowContainer

I have a DaeViewer class that inherited from QWindow, and i want to put it inside QMidArea (QWidgets Only)

For adding new subWindows i am using these code:

m_MainMdiArea->addSubWindow(QWidget::createWindowContainer(newViewer))->show();

So later i want to m_MainMdiArea->setActiveSubWindow() with window name, which one i have.

For this operation i need to have QMdiSubWindow with widget, but i don't know how i can get this widget in this situation.

So before using QWindow, when i use widgets, i compare pointers, but now i can't get necessary pointer becouse QWidget::createWindowContainer creates a NEW widget with this QWindow.

So how i can get a element inside QWindowContainer Trying to find information about this class, and don't find anything useful

Thanks