I opened my project in Xcode 7 beta and I am getting the following warnings which I do not get in Xcode 6:
All interface orientations must be supported unle
I just saw this error and after reading the comments, I surely want to support iPad and multi-window use. This is as simple as checking Device Orientation options "Landscape Left" and "Landscape Right" and making sure that my UI supports these.
Best way I found to test for good multi-window support is to use the resizable simulators, or better in my opinion, use the iPad Pro in XCode 7.1 and actually activate the multi-window feature by dragging from the right. After taking these steps, I my app supports these features and I'm able to quickly see what I need to update or optimize to fully support them.