Create sidebar in mac app with sections

Question

I want to create a sidebar in one of my mac applications. Basically it will look much like the Things sidebar.

Here is the picture that I basically want to recreate:

I can't figure out how to show the "sections" (collect, focus and active projects) and how to have certain items always show up (inbox, today, next, etc...) and finally I would really appreciate if someone would explain how to make the active projects section, with the triangle.

Also I need the active projects section to load from an entity in core data.

I would also really appreciate if you could post an example.

Answer 1

Apple's "SourceView" sample should be helpful with this:

Apple Example