Dev Build 2113 is out now.
Code Folding is in this build, but it's just the basics so far. The relevant key bindings are:
Ctrl+Shift+J (Cmd on OS X): Fold/Unfold selection
Ctrl+K, Ctrl+J (Cmd on OS X): Unfold all
Ctrl+K, Ctrl+T (Cmd on OS X): Fold all tag attributes
Anything can be folded, not just lines: you can see this in action when folding tag attributes. There will be key bindings to collapse functions etc in the future.
There are a couple of new API functions (not yet in the API reference):
Think of the code folding at this stage as a preview: 2113 was released mostly to get a couple of bug fixes out the door.