Open Files are a great new feature in Komodo 8.5. They were already introduced in 8.0 but have received some significant updates since then.
This video walks you through the basics and explains the main purpose of the widget.
You can view the patterns I was using in the video here: gist.github.com/Naatan/9231532
For a more advanced pattern, check out the one I'm using for development of Komodo IDE: gist.github.com/Naatan/9231578