"Gender dysphoria" is the discomfort that comes from being transgender.
https://en.wikipedia.org/wiki/Gender_dysphoria "the term
gender dysphoria applies only to the discontent experienced by some persons resulting from
gender identity issues." And the terms "mental disorder", contrary to what people seem to believe, aren't per-se negative, they just indicate a distress that someone experiences.
That said, I don't agree myself with it being in the DSM, because as most people see "disorder" in a negative way, it just contributes to stigma, plus that distress can also have (partially or fully) social origins and I don't believe it's right to "shift the focus" on the distressed people, it's society that needs to change. It'll almost certainly go away in the next revision though