You can archive a timer on the app right from the home screen by swiping it from right to left, then tapping the "Archive" button that is revealed. When you archive a timer, it does not affect any time entries that you already created with that timer and these entries will still show up in your reporting even though the timer will no longer show on your home screen.

To restore a timer, go to settings > manage content > archived. Tap the name of the timer you want to restore and then select the 'restore’  button.