You can change whether the screen is split vertically or horizontally, or collapse one pane altogether:

The middle button swaps what side the Previewer and your code are on: XAML preview controlsĬhoose whether you want to see your code, the XAML Previewer, or both by selecting these buttons on the split view pane. However, the split can be changed for each file in the editor window. When you open a XAML file, the editor will open either full-sized or next to the previewer, based on the settings selected in the Tools > Options > Xamarin > Xamarin.Forms XAML Previewer dialog. In this dialog, you can select the default document view and the split orientation.

If you want to change the default split view behavior, use the Tools > Options > Xamarin > Xamarin.Forms XAML Previewer dialog. You can open the XAML Previewer by clicking the arrows on the split view pane.