MySQL Administrator can be separately installed from the MySQL GUI Tool Bundle. Oh yeah, did you know that finding and reporting bugs in the GUI tools might win you an iPOD?
Now, about that tip: it's a documented feature, but not well known nonetheless.
Click the "Health" item in the left sidebar, and choose one of the tab pages:
Once you've opened the page, the right-click is your friend in many ways. Just right-click inside the frame enclosing the graphs to add a new graph. A right-click directly above the horizontal line to add an entire new tab page.
Simply right-click inside a graph to invoke a little menu. From there, you can edit the existing graph: