The graphs on the Movie Clip Editor are quite different than most other parts of the interface, even tough they look similar. Think of them informational instead of editing tools.
To view a particular tracker it helps to open the Track section in the numeric panel on the right of the screen.
That will show you the search box for that particular tracker at the current frame. The tracker can be selected directly on the Clip editor window.
But can also be selected by clicking on the dopesheet or on a particular line in the graph.
But unfortunately there is no way to make the cursor jump to a specific keyframe. In the Dope Sheet keyframes are not selectable.
In the Graph window you can select the point for a specific frame, but the normal keyboard shortcut to make the cursor jump to that frame does not work.
The only way to bring the cursor to a specific point is by manually placing the cursor on that specific frame.
Motion Tracking. What do the graphs represent and how are they useful?