Within the Teamwork Timer app, you can add existing tasks from your projects as new timers.
To add a new timer, click the + to the bottom left of the timer window.
When you choose the add timer option, you will then be able to create a new timer by adding a name or select an existing task from your Teamwork site to log time to.
When selecting an existing task for the timer, you will see the option to select the Project and a task list within it.
In the Select Task modal, you can also create new tasks without leaving the Timer app.
You can also drag and drop tasks from your project in Teamwork directly into the desktop app to create new timers.
For more information, see: Logging Time Using the Desktop Timer App