When a work item is too large or too complicated, you can break it down into smaller, more manageable pieces: Subtasks. Subtasks can be assigned to different team members, making responsibility clear. They are also valuable at monitoring progress at a granular level.
Click on "Subtask" at the lower part of the title or click "+" button next to the "Subtasks" fields on a work item’s detail pane, enter the subtask’s title, and press Enter to create a subtask.
Hover on the title that you want to change.
Click the "Assignee", "Start/Due time", "Estimated Workload"(only when enabled) to set each field respectively.
The estimated workload of subtasks (estimated story points, or hours of work) can be automatically tallied as part of the total estimated workload of the parent work item.
Automations is also supported for subtasks. You can either update subtasks themselves, or use subtasks as triggers to update the parent work item.
Examples:
When the subtasks of an {In Progress} {Parent work item} are all completed, modify the status of the {Parent work item} to {Completed} ;
When an {In Progress} {Parent work item}'s {Due Time} is updated, set the {Due Time} of all subtasks to be the same as the {Parent work item}.
Click the icon and rewrite the title.
