If you have, say, 300 pages in Category:A and you want it moved to Category:B it can be a lot of work - which is one of the main reasons that a bot account is useful. With one command it can fix all the pages for you.
Hi. Sulfur and Thisismyrofl are correct -- the only way to "move" a category is to change the category label on all the pages where it is used. If you have text on the category page itself you can move that to the new one.
I was also going to recommend a bot if you have a lot of pages that need moving.
I don't know if this is the case here or not, but some pages that contain very complex coding can NOT be edited with the Visual Editor. If this is the case, when you try to switch to the Visual Editor a pop up should appear and say something like this:
Source mode required
Rich text editing has been disabled because the page contains complex code.
Hi. The visual editor is not available on that wiki (if you go to your preferences you will not see an option to turn it on there, even though you may have it enabled elsewhere). I am not entirely certain it will work with the extensive SMW code the wiki uses. If it is important to you, please send a request in to Special:Contact and we can investigate further.
I suspect Sannse may just already have left for the weekend (it is late Friday in the US). I'm sure she is happy you have found a new idea wiki to work on and are trying not to repeat the mistakes you made at the last one!
I always find that I talk to different people about different stuff -- I think it's normal.