It’s high time you update your macOS app to support the Touch Bar. You’ll need to have some strategy on how to design your Touch Bar interface – don’t just pour any buttons into it. Here’s some tips on how to work this new hardware.
Cocoa’s document architecture envisions that a window should only handle one document. However library-type applications may need one window to handle multiple documents so that the user can easily switch between libraries without restarting the application. Here’s how you can hack AppKit so that a single window handle multiple documents.