One of the breakaway characters in Star Trek Into Darkness was Science Officer 0718, the striking, bald, cybernetically augmented human who manned the bridge with Spock, Uhura, Chekov and Sulu in the second Abrams movie.
Though he didn’t have a lot of dialogue, or even an extraordinary amount to do, fans were drawn to his character and many wanted to see more.
Unfortunately we’re not going to, at least not in Star Trek Beyond. While Gatt’s character was in the first few drafts of the film, he was recently called and told his character would no longer be returning.
TrekCore have the details in the link right here.
If you’d like to read more about Science Officer 0718, you can check out his page at Memory Alpha here.