First create a dashboard with map navigation tree widget. Easiest way is to have few navigation trees of max level and have a short widget height. Take an element from root and try to drag it till the end to switch positions. It is not possible, because there is no empty space. Of course the workaround is to do the other way around. Take the last element and drag it in the place of the previous one. It works, but same should be achievable without such hacks. So the proposal is to add an empty line at the very end of widget in the edit mode.