I can't figure out how to move them back out again to the root level.
You can drag and drop sub keywords to other locations higher or lower in the nested folder but you don't seem able to drag from sub level to root level.
The easiest workaround would be to have a regular Back up of the list (pop menu from icon top right keyword panel: export keywords) and when not having added new words just use clear and import the back up to restore.
If you did edit the list you can choose to export current list and with a simple text editor make the changes for keywords and sub keywords you want, save and then use again clear and import to retrieve the correct list.
