Make Manual Sort button a toggling button with an indicator.
I use manual sorting a lot.
While in a task list in Manual Sorting mode, I often find myself, intuitively, hitting the Manual Sort button again, with the expectation that it will result in toggling back to Normal mode.
However, it does nothing.
The only way to exit manual sort mode, is to hit the arrow in the top left of the screen.
My request would be to make the manual sort button toggling manual sort mode on and off, preferably with an indicater (a highlight for instance) whether it's on or not (although the text "Drag the tasks to reorder" also functions as a visual clue that manual sorting is active).
I think that would be a superior UI principle, the user doesn't have to remember two distinct places on the screen.