Sarah Mason, inventor of the continuity script, first script supervisor

Probably the key on-set invention of the talkie era is the role of script supervisor, of the notion of keeping track of continuity and the continuity script, which records in code each take, its length, and differences in lens, exposure, subtle details in continuity (when a sip is taken, which hand holds it).

Strangely she left no records, was rarely if ever interviewed, and her invention was overshadowed by her own ability as a writer and her domineering husband who took credit for her work.

Notice the Columbia link makes no note of her core contribution to the film industry.

https://en.wikipedia.org/wiki/Sarah_Y._Mason