Marcia Lucas in fact won an Oscar for her film editing of Star Wars. George Lucas was up for two that year and won neither (he was beaten out by Woody Allen for both of them). He has still not won a competitive Oscar.
The entire “Death Star approaching Yavin 4 to blow the rebels up” was created wholecloth in editing to add needed tension to the attack on the Death Star. They reuse the same “pull the lever to fire” shot both times they attempt to fire the Death Star laser.
To be fair, Marcia Lucas worked on the original edit of the film (the one everyone hated). It was completely reworked when the studio brought in Paul Hirsch and Richard Chew.