According to this: https://en.wikipedia.org/wiki/.NET_Framework#.NET_Core it shows that .net core supports four-cross platform scenarios:
What I want to know is, does the Visual Studio for Mac IDE support creating desktop 'universal apps' that can be executed on a mac system?
OR
Is this only supported in the Visual Studio IDE for the Windows platform?
Currently you can't use UWP on the MAC
as UWP supports Windows 10 eco system (Win10,IOT,XBox) but you can use .Net Core to build cross platform console app and asp.net core to make web services and webapps
.