Disney’s most prolific inventor, Lanny Smoot, is behind some of the company’s most advanced tech, from “Star Wars” lightsabers to “magic” floors. Disney’s long-secretive R&D lab helps build creations that are crucial to Disney’s $60 billion investment in the division that includes its theme parks. Smoot gives WSJ a behind-the-scenes look at his creative process and the technology that could make the next must-see attraction for Disney parks.