I believe in DS9 Mission Gamma: Cathedral that we revealed that Ro Laren had previously had both male and female lovers.
IIRC, that wasn't in MG but in
Abyss. She mentioned (in internal dialogue) a list of past lovers, and one of them was called Dana. Which may be a woman, but not necessarily.
I seem to recall(dimly, and I'm open to correction)that Prynn Tenmei briefly considered "chatting up"one of her female Academy classmates when she was having little sucess with the males.
No, that definitely happened. But then her attraction to Shar, who is not entirely male, shows that she's open-minded about such things.
* The one someone was thinking about from
Tales from the Captain's Table is from DRG3's "Iron and Sacrifice," where one of Captain Sulu's ancestors was a gay male couple.
* There's also Ensign Stadi, the quickly-killed
Voyager helm officer from "Caretaker," who was established (either in the
Caretaker novelization or in KRAD's
Brave & the Bold, I forget which) as having lesbian parents.
* And there was the lesbian Klingon in
Taking Wing who felt up Christine Vale's ass (onboard, as I never cease to be amused by, a ship called the
Vaj).
* I seem to vaguely remember (from
Section 31: Rogue) a brief passing mention of an ex-boyfriend of Hawk's, previous to Keru.