WinUI3 uses the CreateWindow function

[ClearSeve]

Through get_WindowHandle method gets the window handle and creates the window

    void SetOpacity(HWND hWnd, int nOpacity)
    {
        SetLayeredWindowAttributes(hWnd, 0, (BYTE)(255 * nOpacity / 100), LWA_ALPHA);
    }

    MainWindow::MainWindow()
    {
        InitializeComponent();

        auto windowNative{ this->try_as<IWindowNative>() };
        HWND hWnd{ 0 };
        windowNative->get_WindowHandle(&hWnd);

        GdiplusStartupInput gdiplusStartupInput;
        ULONG_PTR gdiplusToken;
        GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);

        auto sImage = GetFullPathToAsset(L"butterfly.png");
        HBITMAP hBitmap = (HBITMAP)LoadImage(NULL, &sImage[0], IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
        Bitmap bmp(&sImage[0], true);
        Status status = bmp.GetHBITMAP(Gdiplus::Color(0, 0, 0), &hBitmap);

        HWND hWndChild = CreateWindowEx(WS_EX_TRANSPARENT | WS_EX_LAYERED, L"static", L"", WS_VISIBLE | WS_CHILD | WS_BORDER | SS_BITMAP | SS_REALSIZEIMAGE /*SS_REALSIZECONTROL*/, 10, 10, 400, 400, hWnd, NULL, NULL, NULL);
        SetOpacity(hWndChild, 100);
        SendMessage(hWndChild, STM_SETIMAGE, IMAGE_BITMAP, (LPARAM)hBitmap);
    }

You can see that the window has successfully created and displayed a picture, but this button is below the window just created. Is there any way to put the button before the window just created. It can be changed as long as it can be realized reference material: https://learn.microsoft.com/en-us/answers/questions/1115740/can-we-use-both-winui3-controls-and-win32-controls

[ClearSeve]

It feels like this is the drawing area created using createwindow

My own display is incomplete

[AzAgarampur]

Xaml islands for WinUI 3 aren't supported yet, you can use WinUI 2 XAML islands to do what you want and have a separate child HWND for xaml content.