Visual Studio 2017 for Mac is actually another beast from Visual Studio for Windows. As you know, this is initially based on Xamarin Studio, which in turn is extended to MonoDevelop.
Simply put, the extensions you find in the Visual Studio Marketplace are not compatible with Visual Studio 2017 for Mac.
VS2017 Mac , . IDE :
Visual Studio >
. - , MonoDevelop http://addins.monodevelop.com/

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