How is it possible to manually sort tasks?

(In your blog post on Nov 3 about new features, I notice that about half-way down you refer to manually sorting tasks, in a graphic, but I cannot work out how to do this.)

When I click on the mosaic patter to the left of a task (in the web version) a four-way arrow appears, which suggests I should be able to move a task, and, yes, I can move it to another section (e.g. Tomorrow or Someday) but if I try to move it higher or lower in the existing list, it refuses to move.

It is (obviously) important to be able to organise tasks in the order that I choose, so hope that I am missing something here and it is really quite easy to re-organise them manually. How do I do it, please?

T