Edit Task Details - Navigation and Ease of Use

Does anyone have the following issue:

You go to Manage Project Plan and Edit TAsk Details, at the top there is a Task Number dropdown. In this particular example, I am modifying asset assignments at task level. When I modify a record, save, the dropdown in Task Number changes, it does not give me all of my available tasks, does not give me all my chargeable tasks.

I am attempting to make map out the most efficient user process and was wondering if possibly I am misunderstanding the usage of this Task Number dropdown. Users absolutely dislike the task level assignment methods when capitalization is linked to lowest level task