I agree with this request. The greater the number of categories, the more unwieldly it becomes when you make any change. Some kind of batch processing would be very helpful. (You edit category names, move categories into another location, etc, then click on "Update" and everything is done at once - rather than having to wait a long time for each change to take place.
I'm not sure I understand GauGau's objection about categories being "nested infinitely", thereby making this unfeasible. The same is true of Albums, yet you can batch edit all albums in the same category as much as you want and then update them all at once. You should be able to select a parent category, and then batch edit all immediate child categories in the same manner.