Setup single project for both Mobile and desktop

I currently have a project that I can publish to Desktop & Mobile.

It is a Mobile project that does work on Desktop when published.

What it cannot do is Debug as a Desktop.

I cannot create a configuration debug profile for it as the Configurations Panel will not let me add a Mobile Project to a Desktop configuration.

I repeat, it works fine when published complete with NativeWindows and other Desktop capabilities.

I should clarify that I can debug the app as a Mobile Device on the desktop - but not As a Desktop App.

Is there a way to add a Desktop Debug Configuration to a Mobile project?

I realize I could create another project as a desktop app  and share the resources between the two but that is not question.

Thanks for reading.