the lesson order
can change the lesson, sub-lesson order by selecting a group on the left hand
side panel, and then pressing [change sub-lesson order] on the right hand
side panel. You will then see a menu in the right hand side panel with the
current order of the sub-lessons and sub-groups of the currently selected
group. You can directly edit these numbers, therefore changing the order.
After you are finished, press 'enter'.
conclusion: You will see the result of the reordering in the left hand side panel. You can repeat this operation as many times as you like.