Note: the Onscreen Control no longer works in FCPX equal to or later than 10.0.6 — at least not the way it used to [Apple changed the “dominance” to the Text object.]
The same tools you have in the storyline (Select, Hand, Trim, Range, etc.) are available in the Viewer. Changing the Tool to anything other than Select (A) or Zoom (Z), will give you access to the OnScreen Control.
You will need to get used to this because a lot of templates depend on OnScreen Controls.
Using the Hand (H) or Range (R) tools are the easiest and accessible by the left hand, leaving your right hand free for using the mouse (or other control).
Animation can also be accomplished using the “Center” parameter.