Sub-Tasks Don't Actually Link to Parent Tasks and Changes Disappear

Problem:

You can indent tasks to visually suggest a sub-task relationship, but they aren't actually tied to the parent. On top of that, any changes you make to indented tasks disappear when you leave the task tab. 

Impact:

The sub-task feature basically doesn't work. You can't build any real task hierarchy and anything you do gets lost anyway.

Request:

Make sub-tasks actually link to their parent task. When the parent gets moved, sub-tasks should follow. Changes to sub-tasks need to persist.