TBMInspectorView is a copy of the Xcode 5's inspector view. It is pretty easy to setup and should used as the documentView of a NSScrollView.
If you're using CocoaPods simply add the following line to your Podfile
pod 'TBMInspectorView'
else add all .h and .m files you find the Classes
folder to your project.
Code from the example project for setting up the inspector view:
TBMInspectorView *inspector = [[TBMInspectorView alloc] initWithFrame:NSMakeRect(0.0, 0.0, NSWidth(scrollView.frame), 0.0)];
[inspector addView:view1 label:@"View 1" expanded:NO];
[inspector addView:view2 label:@"View 2" expanded:YES];
[scrollView setDocumentView:inspector];
Supports 10.6+, not tested in Autolayout environment yet
MIT