I've updated to the latest version of Xcode and VS for Mac, and when I attempt to add some new controls to the screen I can add the controls themselves, but no matter what I do can't view/find the 'viewcontroller.h' file to assign an outlet.
Step 4 under 'Adding an outlet' here:
... is no longer possible as the menu options have changed under the 'automatic link'. So either the documentation is out of date and I'm missing something or there's some kind of issue with the VS / XCode link.
FWIW, this is a project that I've successfully been editing using the same method for some years now using Xamarin Mac, so it's a bit frustrating when such a basic piece of functionality has changed in a way I can't work out how to use it or it's broken.