What will house it all

You can switch tabs, but some prefer a legacy "views" mode, we needed to surface how to switch "views" of a tab. Very similar to spaces in OS X. We rolled up that capability into the mode switcher, the blue icon being a mode of the work area below. There is another mode icon on the far right (outside the crop) that, when clicked, opens another set of capabilities per the mode and hides the capabilities that go with the blue icon mode.

Gotta love throwing multiple features into one UI element.