Using the mini timer
The mini timer always stays on top, so you can keep track of where you are in your session.
Just click the clock icon in the right hand corner. When you need to call the main timer back just click on the timer display, you can do the same thing to make it go away too!
You can also change a setting in the preferences to enable the main timer to automatically minimize when you open the mini timer and as above just click the mini timer time display to bring back the main timer.