Reordering Tasks in a Task List

Unable to reorder tasks in a Task List. There is a command 'Reorder Task List' but nothing happens when we click on it, except that the command changes to 'Save Task List Order'. When we click on Move Task arrow on the left of checkbox of a task, we get a dropdown list of task lists.

Bug affects preparation of tasks of a task list that have to be in the order of their execution.
Narayan