Enable the tree hierarchy view, you can organize your project work by mapping work items into the hierarchy.
To enable the tree hierarchy view, click the
icon on the upper left. The default hierarchy will display as:

You can add multiple hierarchies in the view and custom the grouping of work items.
Click the icon next to the hierarchy to change how work items are grouped.

Click the shortcut icon on the right side of the table to expand/collapse the tree view.

You can add subtasks directly by clicking + between rows in the tree view of the subtask hierarchy, quickly breaking down the work into smaller deliverables.
