To make it easier to work with tasks, you can select one or more and perform actions on them. Here are some selection methods you should know about.
Select a single task:
Click to the right of a task’s name to select it.
Select multiple reminders:
Press and hold the Command key, and then click on the tasks, as above, to select them.
Select all reminders in a list:
Select one reminder, then press Command + A to select the others on the list.