Right, my earlier post was incomplete: copying -- as opposed to moving -- an address book entry has continued to work as before, under all OSes from W2K up to W10. 

It's the single step moving protocol which ceased functioning a few PMail versions ago. 

Many mysteries . . .  voodoo. 

Is there an easy way to move addresses from one book to another other than by exporting/importing?

Up until three or four PMail versions ago -- I don't know precisely when -- an address book entry (or entries, following the usual CTL-click or Shift-click protocol) could be moved from one address book to another in a single motion by click-drag while holding down the ALT key.  Then that just stopped working, at least for me, although I've seen nothing posted or published about this, nor any reason(s) given. 

So at this point it would be a two step process: click-drag, then go back to point of origin and delete. 

- Christopher Muñoz 

In 4.70, an address book entry can be copied by dragging it to another address book -- with or without holding down the ALT key. I agree that no key combination moves the entry in one step. (Win7 x64)