It's possible to select multiple tasks by clicking on the checkbox in each task's row you want to select.

To select a single task: Click on the task's row.

To select multiple tasks: Click on the checkboxes in the tasks' rows.

Also, the shift key can be used to select a group of tasks at once. Here's how:

1. Click on the first task that you want to select.
2. Hold down the shift key.
3. Click on the last task that you want to select.
4. Release the shift key.

You can also de-select multiple tasks in this manner.

Lastly, the select tool can be used to perform some quick selections such as All, None, Due Today, Due Tomorrow or Overdue