Was visiting a friend who was playing a video game on his iPhone, and wanted to share it with a larger group. My mind was blown when he plugged it in to his mac, opened QuickTime Player.app and chose File > New movie Recording, then clicked the arrow and chose his iPhone as the source. Result: full screen iOS screen shows up on his mac (with sound).
I know you can use SharePlay to share iOS to macOS but this requires the latest macOS, and runs over wifi - the Quicktime Player trick works with older macOS and has better performance since it’s over USB.
I could see how this could be useful for development and debugging.
Combine this feature with Mail.app, Flags and Smart Mailboxes and you can set up a miniature organizing system. If you look at the Flagged mailbox, you will see different colored flags. You can rename these to create a “ToDo” system. Here’s mine:
I have set up keyboard shortcuts for each of these, which are now muscle-memory. So I can easily look at each incoming email and decide : Junk? Delete? Keep? DoNow? DoSoon?.. with a single keypress.
I suspect that’s intentional. Because the UIState is embedded in binary projects if it ever became corrupted, holding Option down will skip the uistate data. That existed long before apple decided that Option should close the previous window.