Delete tasks on task board
On the task board, click and hold on the task that you want to delete.
Notice the red bin that appears.
Drag and drop the task into the red bin.
Confirm that you want to delete it and the task will be deleted.
Delete tasks in task list
Go to the matter or workspace task list
Select the check boxes next to the tasks that you want to delete and click on the 'delete tasks...' button.
Confirm that you want to delete the tasks and then they will be deleted.