Microsoft just announced a new cross-platform editor that has many of the features of Visual Studio called Visual Studio Code. I downloaded it on my Mac to try out with a Xamarin.iOS project and see if it works. I was pleased discover it works out of the box (as far as I can tell on a first look).
Visual Studio Code works against files and folders. When you open a folder where a Xamarin.iOS project lives, all the files load fine and features such as links to references and even intellisense on iOS classes work great.
Here’s a class that implements a UIView subclass for example showing intellisense on CALayer:
You can download Visual Studio Code at: https://code.visualstudio.com/Download