I can't seem to get the subtask feature to show up

I can't seem to get the subtask feature to show up

"Making an existing task as a subtask: When you mouse-over the task name, you will find the Indent arrow to the left of the task name. When clicked, the existing task will be converted as a subtask for the task just above it."

I don't see the Indent arrow or have an option to make a task a subtask.  Any ideas?

Thanks!