On Friday I cranked this out:
The key feature here is the ejection angle of the maneuver node. It's a feature I've wanted since I first began interplanetary travel within KSP. It's crucial, IMO, for effectively using tools like alexmun's Launch Window Planner and one of the reasons I named it "Precise Node". I still need to test the angle to retrograde (when the angle is negative, it is angle from retrograde) since I'm not entirely confident with the math, but that won't take too long.
Once I'd written the feature I figured I might as well go full bore and write a proper KSP mod to replace the key functionality of the mod I'm using (no reason to have duplicate mods) so ... future plans include additional +/- buttons, and possibly textboxes, for the delta-V stuff and "multiplier" buttons for the +/- buttons (so you can do 10 at a time or 0.01 at a time, for instance, but they'll be global to all buttons). Right now it only works with the first maneuver node but it shouldn't be that hard to allow you to page through nodes. And, of course, adding a hotkey to open the last edited node widget if needed (with an editor window that's always open I don't really see a need for it, though).
I've already had one inquiry into releasing this and was wondering if there were any wish-list features that people have for maneuver node editing? I know that people want numpad editing, for instance.