With breadcrumbs you can see and easily navigate the hierarchy of tasks and sub tasks.

Breadcrumbs are located at the top of the task.

The first position of the breadcrumb is the List, the second position is the parent task, and the third position and beyond are for sub tasks.

Note: The breadcrumbs will display up to three levels by default. When you go beyond three levels it will always show the last three levels in the path.

You can click the down arrow icon at the start of the breadcrumb at any time to see the full path to the task. This menu will show you all paths that lead to the task, including the board name. 

If the task has Mirrors, additional paths to those mirrors will show in the breadcrumb dropdown menu.

In this example, the task is a standard task on a board. However, it has two Mirrors on other boards. Because of this, there will be three paths leading to this task.

If a Direct Assignments is assigned to you, instead of including a list in the breadcrumb it will say Direct Assignment like this: