The IMDB "uncredited editor" credit is just put in there by a fan. It doesn't mean anything. I mean he is the director and a former editor of course he is going to be involved heavily with the editing, just as Ridley Scott is a former production designer so he is always heavily involved with production design and picks fabrics and stuff for his costumes.

As for Marcia Lucas, i agree--i think it was Speilberg or Wilard Huyck or someone who once said that Marcia was "George's secret weapon," and its very much true. People make a big stink about Gary Kurtz and how when he left the franchise went downhill but his creative involvement is heavily, heavily exagerrated--the real loss was 1983 when Marcia finally left Lucas.