A mouse friendly editor has been on the wish list for longer than I want to admit. The Do-more controllers themselves became so much of the focus, the long planned editor overhaul has just kept getting pushed. There are a number of slightly embarrassing things in DmD (no drag and drop, no true undo/redo, 16 character names, etc) that we really want to fix, and once BRX gets solid, we'll be able to move back to working on those things.
I think we added single instruction copy/paste in 1.4, so it's a little easier to get it moved. Ctrl^C on the instruction and Ctrl^V where you want to put it, then Delete the original.