How to leverage designer when using a ViewModel fi

Question

I have some xaml like:

<ContentControl x:Name="MyContent" />

and then on my ViewModel there is, of course, a MyContent property which references a ViewModel. Then Caliburn does its compositional magic.

This is great, but in design time I can't see the composition. I see 'most' people raving about the view model first approach, but I'm a little baffled as to whether there's a way to leverage the designer when doing this that I haven't yet realized or do all the vm first people just live with the fact that they have to run the application to see what it's going to look like?