Extending an editor control

Hey guys,

I've been extending the editor like crazy recently, and it's been ridiculously easy, I do have a simple question for you though, can I extend a Unity Control?

For instance, extending the functionality of the button, or the scroll view?

I'm trying to create something that looks and works similar to the animation window, however it's not as simple as just placing buttons, as a basis, I want to start extending the scrollview.

I'm quite happy creating custom windows, editors, context menus and title bars, but there must be a way to create new controls?