How do you re-order categories?

Hi, I must be missing something obvious here, but I can't find a simple way to change the orger of categories on a page. On any one day I might have three or four category entries in the right hand pane and I'll enter them as I think of them. I may then want to put them in a particular order, of priority, chronology, etc. At the moment I have to "Change this text", cut, delete entry, enter category again, paste, in order to move an entry to the bottom of the list (and I have to have the final order I want them in determined before I start re-ordering). This is very cumbersome. What would be ideal would be an additional two items on the right-click menu for category headings: "Move this entry up" and "Move this entry down".
But perhaps there's an existing method and I've just not found it. Thanks anyway for an invaluable application.