On this tutorial:
http://www.leadwerks.com/werkspace/page/tutorials/_/editor-interface-r1
It says: "By clicking with the left mouse button in one the viewports, we make it the active viewport."
It is not obvious when clicking in the different viewports which one is active. The Perspective view always appears to be active. There is no visual indication that anything happens. That only reason you can tell that it worked is because the brackets (][) work to change the grid size of the correct window.