The first season on this record carried three headings. Across all seventy-two seasons there are fifty-four distinct ones. No season carries them all, and several exist for only a few years before disappearing again.
The pattern is consistent enough to state plainly: a heading appears once enough productions employ a specialist to make the comparison meaningful. Projection design arrives in 2007-08 — not because nobody had projected anything before, but because the equipment became standard enough that the work could be judged against itself.
Fight choreography, first awarded in 2016-17, is the clearest case. Stage combat is as old as the stage. What changed is that enough productions hired someone whose whole job it was. The heading follows the specialism; it does not create it.
The 1970s ran a set of headings this record shows nowhere else: Most Promising Playwrights, Most Promising Composers, Most Promising Set Design. They existed for a handful of seasons and were dropped. A category can be a bad idea and still be part of the record.
Splits are the other half of the story. Scenic design divided across musical and play in 1995-96, lighting in 2008-09, sound in 2009-10, costume in 2015-16. Each split says the same thing: the workload in the two forms had stopped being comparable.
Read the fifty-four headings in order of first appearance and you have a rough history of the trade's own priorities — what it valued, when it noticed, and what it briefly thought mattered and then decided did not.