Since the categories that Organizer creates are desktop folders and that contain shortcuts to apps (not the applications themselves), you can add or move items as easily as copying shortcuts between folders.

Moving Items
To move items from one folder to another, just use Cut, Copy and Paste (Ctrl-X, Ctrl-C, Ctrl-V) to move one or several shortcuts from one folder to another. Cut, Copy and Paste can be done from Power Drawers menus or from an Explorer window for a folder. You can also put a shortcut to the same app in more than one folder where that makes sense. 

Renaming, Moving Folders
You can rename the folders created by PowerOrganizer without disrupting anything. If you think of Desktop Publishing as Word Processing or name it another language, simply rename the folder through Explorer or Power Drawers as you would any other folder. Renaming does not affect it's ability to classify new items into those folders. You can also move the folders around. For example, if you use Graphics apps a lot, you can get faster access by moving that folder to the desktop instead of being a subfolder of Programs.

Creating Subfolders
If you many apps in a desktop folder, you can create subfolders to further organize the apps. From the Power Drawers menu for a folder, select the New Subfolder.. item to create a new subfolder. Then copy any desired shortcuts into the new subfolder using Cut, Copy and Paste commands (Ctrl-X, Ctrl-C, Ctrl-V) either from a Power Drawers menu or the Explorer window for that folder.

See PowerOrganizer in the Online Manual for more details.