In the top right-hand corner of your dashboard, click on the Add Report button. Then on the left-hand side navigate to Sales > Productivity. You'll find a report that's specific to tasks there, I would just add that in:
In the top right-hand corner of your dashboard, click on the Add Report button. Then on the left-hand side navigate to Sales > Productivity. You'll find a report that's specific to tasks there, I would just add that in: