I've seen a few feature requests kicking around for various ways to help people know what the parent task is for any subtask.
What I'd like to see is a hove method put into place. In my mind it'd be nice if one could hover over the subtask icon and the name of its parent task would show in the hover area.
This reduces the need for additional screen real estate needed by other requests while still allowing one to quickly put any subtask "into context".
Sorry but I wouldn't like to see it implemented this way.
I'd prefer to see the parent task name in smaller sized & colored font (perhaps even in brackets) alongside the subtask name.
The reason is that this means the user can glance at a list and immediately see subtasks with their parent task relationship, and when a list is printed it will also be displayed.
If you have to hover over a subtask manually then you might as well just click the subtask icon to display the parent, which you can already do now.