In order to add a task to a shift, you must choose from your existing list of task templates, but it's easy to modify an assigned task for just one shift. This wasy you can provide extra details or add/remove subtasks.
There are multiple ways to edit a single task.
From the task list:
Under the main Tasks page, there is a tab for Shift tasks. This will list all your assigned tasks (those attached to a shift). These can be edited individually by:
clicking on a task in the list, then clicking the Edit task button
clicking the options button (3 dots) next to the task, then choosing Edit.
Note: Managers can't edit tasks that are not scheduled in their location.
From the schedule:
When you click on a shift, you will see any assigned tasks. Click on the task title to open the details, then you will see a link to jump to the task view so you can edit it.