Windows 8, open OneNote and pin it to the side of the screen.
You can now drag and drop from the left side of the screen into OneNote.
What would you have to add to this to get Courier-like application (genuine ignorance on my part, I never followed Courier in detail).?
First, you'd need to add more of a book-like visual metaphor to OneNote. Then you'd have to add a "pocket" that sits between the two panes and allows you to change what's displayed on the two panes without losing the content stored in the pocket.
The only problem is that Metro is moving away from using a UI with graphical metaphors in favor of one that's more content-focused UI and devoid of graphical metaphors.
This interface is about as anti-Metro as you can get.