This site is being deprecated.
Please see the official X‑Plane Support page for help.
This is discussed briefly in our video on the new UI (at about 4:40). We have redone how multimonitors work for v11 based on a lot of feedback we've gotten over the years with v10. We'll have more specific information later on as we're planning to do a feature on it on our site.
This site is no longer being actively maintained.