The State Preservation and Restoration system is well documented here: Preserving Your App’s Visual Appearance Across Launches.
But what is not well known is that there is a secret preference to enable debug logs.
Let’s say you want to have a different behavior in your app depending on whether you build it in Xcode or you perform an Archive. And you want this behavior to be done at compile time. Note that the use of different configurations is not what is wanted.
OS X 10.11 ‘El Capitan’ added a new feature to Mail.app Swipe to manage your inbox:
Swipe to manage your inbox.
Now you can take care of your email with a swipe, just like on your iOS devices. Need to triage your inbox? Swipe right to mark an email as read or unread, or swipe left to delete. You’ll be focused on what’s important in no time.
I find this new feature extremely annoying as I keep triggering it by accident. Sadly it seems that there is no preference (even secret preference) to disable this feature. But the good news is that Mail.app supports plugins.