Hello @XB121,
Unforturnately Designer View is not supported for now in WinUI3 for XAML files. You can track its status on Github:
https://github.com/microsoft/microsoft-ui-xaml/issues/5917 https://github.com/microsoft/microsoft-ui-xaml/issues/3656
You can also check this question, https://stackoverflow.com/questions/70292470/where-is-the-designer-view-in-winui-3.