938 votesjoshcoady commented
Just make sure you click on the actual name of the task--dont click the checkbox. Clicking the checkbox itself will mark the task as completed and remove it from the list.joshcoady commented
I believe this feature is already implemented. I use the popup and when I start working on a task, I click on its name, call it Task A. Then, if I need to start a different task, I click on Task A to stop its timer and then on Task B to start its timer. When I am done with Task B and ready to go back to Task A, I click on Task B to stop its timer and then on Task A to start its timer up again.