- Create a script in Unity that has two or more compiler errors
- Set your default code editor in Unity's Preferences to Xamarin Studio
- Double click on one of the error messages in the Editor Console window to have it open Xamarin Studio and show the script that generated the error
- Remove the cause of that error and switch back to Unity so that the script gets recompiled
- Double click on another one of the error messages to go to the script that has an issue

Expected: the already open Xamarin Studio shows the script with the error
Actual: an additional Xamarin Studio instance gets open with the script (every double click in the Console window will just open a new instance of Xamarin Studio)