I sent a suggestion a while back about using levels as the current view. Meaning, you have a Parent Level, which is what we are used to seeing in the task list. While I love the dropdowns on the first level, I’m sure that will get kind of ugly and crazy if you are 3+ levels deep. So I suggest the interface shift from Parent Level, to subtask level, in that main task list view. For example: And this may be hard to grasp using words!
The interface could have level buttons (based on how many subtask levels are in the current project.
[<] [>] [PL] [L1] [L2] [L3]
[PL] is the Parent Level (the level we are used to seeing in the task list)
When I press [L1], the PL level shifts to the left, revealing the subtasks at Level 1. This presents them the same way the tasks are presented at the parent level. Same functionality. Once I’m done, I can hit the [PL] to go back to the parent level. Of if need be, I can go deeper by hitting one of the other subtask levels [L2], [L3], on and on. The [<] and [>] are just ways of drilling down, without having to have all the [L1]…[L9], etc… So you can maybe do the first 3 levels, and if people want to go further, they can use the arrows.