Star Trek is generally considered a traditionally episodic franchise simply owing to its genesis in the years before serialized storytelling.
Still, the writers and producers were able to sneak continuing arcs and subplots into the various spinoffs and series with greater frequency as the franchise aged and we are now in the era of the ten hour movie-style structure of Star Trek: Picard.
We can point to the Klingon Civil War, the Dominion War, the Kazon's pursuit of Voyager, and the Red Angel storyline as successful ongoing plots, but there are a few subplots and arcs that Star Trek has either failed to deliver on, outright forgotten, or mercilessly jettisoned.
Here are a dozen Star Trek subplots that boldly went nowhere.
12. Worf And Troi
The romance between Star Trek: The Next Generation's Lieutenant Worf and Counselor Deanna Troi was a major plot point in TNG's final season, in the episodes "Parallels", "Eye of the Beholder", and "All Good Things..." But the flirtation dated back as far as season five when the writers saw that a Worf / Troi pairing worked in the episode "Ethics".
What followed were an alternate-timeline marriage and a hallucinatory hookup before the two finally made it real and official in the series finale – which also diverted into an alternate timeline in which Troi was dead and Worf never got over his lost love.
But while the series finale of TNG began with an almost kiss, the next time audiences saw Worf and Troi in Star Trek Generations, the two about-to-be-former Enterprise-D officers had apparently split up offscreen in the intervening months.
By the time of Worf's arrival on Star Trek: Deep Space Nine and his eventual marriage to Lieutenant Jadzia Dax a couple years later, the Worf / Troi thing wasn't mentioned. Star Trek: Insurrection featured a subtle nod to the pairing when Troi finally reignited her fling with Commander Riker and Worf grudgingly observed that they'd always had feelings for one another. But calling that an acknowledgement of Worf's own romance with Troi is kind of a stretch.
For her part, Marina Sirtis aka Troi didn't like the pairing, saying that it hurt Worf's character. And while Michael Dorn seemed okay with it, Imzadi himself, Jonathan Frakes, called it "ridiculous". The writers seemed to agree it was a failed experiment and the Worf / Troi romance subplot was never mentioned again. Troi wasn't even invited to the wedding.