As a matter of interest, up until I don't know just when -- the rollout of PMail V3.x, perhaps - ? -- it was in fact possible to move an address book entry from one book to another, in one operation, at least under an OS prior to XP.  

Holding down the ALT key while dragging & dropping moved the entry; same with the CTL key just copied the entry.  

Why this function was deprecated I do not know.  Perhaps the ALT key was being captured by another process, or perhaps too many errors resulted.  Or perhaps it simply was a byproduct of other OS changes, without intention.  

I miss it, myself.  Now it takes two steps to do what formerly could be done in one.  

- Christopher Muñoz

As my address book enlarges I want to sort it out, but I cannot see a way to drag ad drop addresses from one book to another.  If it is not already a feature, could it be added please ?

Well !  Isn't that always the way.  As soon as you ask, you discover that it does drag and copy, though not drag, delete and drop, so I still have to go back to the original book and delete the duplicate.  Maybe a right-click menu would help with the usual, cut, copy, paste, delete options, the last avoiding the time consuming business of moving the mouse up to the Entries box to select delete and then click on confirm.  Maybe all deleted addresses could be automatically moved to a trash bin for final deletion, then the route via the Entries box with its confirmation requirement could be removed.