WinUI 3 / .NET MAUI XAML designer is not supported in Visual Studio 2022. To view your WinUI 3 / .NET MAUI XAML UIs and edit them while the app is running, use XAML Hot Reload for WinUI 3 / .NET MAUI. For more information, see the XAML Hot Reload page.

https://learn.microsoft.com/en-us/visualstudio/xaml-tools/xaml-hot-reload?view=vs-2022