Thanks for the feedback!
The Show/Hide labels are copied from the Show/Hide labels in the Finder, iTunes, Xcode, and other Apple software. I find them less cluttered than disclosure triangles.
Moving them to the left of scroll bars is a good suggestion. I see that Apple do this when scroll bars are set to show "Always" - is that the preference that you're using (in System Preferences: General)?
I've logged this as a task.