Just double click on the CM name. Not sure if this is documented anywhere.
This is just to prove that SolidWorks' interface is really intuitive. A student in my last Essentials class, got his CM undocked and asked me for help. When I got to his desk, before having a chance to show him how to drag the CM back, his finger did automatically a double-click on the CM name and the toolbar jumped back to its anchor.
I asked him how did he know to do that. The answer: "It felt natural".
It also shows that an instructor always learns something valuable during a training course.
Note: Thanks to Rob Kerslake for doing what he felt was just "natural".