Within Teamwork Projects, you can pin task lists so they remain open on your project.

By default, the task list will be hidden from the main tasks area when all tasks in a task list have been completed. You will see it listed in the panel on the left under Completed Task Lists.

To pin a task list, hover over the task list name in the Tasks area, and click the pin icon on the far right. 

Once the task list is pinned, it will always remain in the Tasks area unless you unpin it.

To unpin a task list, just click the pin icon again.

Note: Only administrators or users with permission to update task lists can change this setting.

For more information, see:  Creating a task list