I always got the impression that Luke had returned to Dagobah in between films and completed his training. As said, there is a feeling of a decent amount of timing having passed (on the order of at least months to half a year or more) and a distinct shift in Luke’s manner, maturity and mastery on some level of the force. It would be cool to see a few scenes like Luke constructing his Lightsabre but in my mind theyre completely unnecessary and I don’t know how you’d integrate them into the movie anyway without completely changing the tone of the movie, especially at the start with the rescue mission at Jabba’s palace.

.Val