I see where you’re coming from with Dax (the Curzon->Jadzia transition), but I’m not convinced she is actually trans.

As far as I’m aware, Dax (as a Trill symbiote) is genderless, and Jadzia is a cis-woman.

Also, if we conceptualize her as trans, then Sisko calling her “old man” starts to sound like hate speech, but neither of them treat it as such.