“Young Frankenstein” is still in tryouts in Seattle. But already Mel Brooks and his collaborators are looking at their next project. “It could be ‘High Anxiety’,” Brooks collaborator Thomas Meehan said of the 1977 Hitchcock parody at the ‘Young Frankenstein’ opening-night party. “That’s the leading candidate. We have such a great time. We don’t play golf. We like to work.”