Well, the Mol storyline is she escaped Moonrise by signing a contract with Raphael and hoped to outsmart him by using the contract to take over the Guild in BG yet find a workaround the payment. In fact, when you return Raphael's contract to her from the House of Hope, you have to not mention you dealt with Raphael or she'll be furious you removed the patron that was gonna make her leader of the Guild, and will not join you in the final battle while stating that when she does take over the Guild in the future, the guild won't take kindly to you, despite what you did for her and the tiefling kids in the past.
The tiefling story is more or less resolved by Act 3 outside Dammon being abandoned as a solution to Karlach. Roland, Kai, and Lea become a family and Roland the master of Ramazith tower, the tiefling kids get jobs as paper boys and salesmen, the tiefling couple are in the refugee camp since they don't have a pass, but will join in once the events of the final battle resolve as the blockade will be lifted. Alfira is resolved to start a music school while Lakrissa helps her financially with her job as a barmaid. The only truly abandoned storyline is Zevlor and his hellriders, but that's because they basically massacred most of the tiefling soldiers in Act 2, so there's literally like 3 Hellriders left including Zevlor, and Zorru can't even be called a hellrider, so it's Zevlor and his liuetenant lady. Even before then, Zevlor told her he fully intended to not pursue a military life in BG and suggested she did the same back in the grove.
Really, it's the hag coven storyline and the Gondians+Dammon fixing Karlach's engine that feels more of a discontinued story from Act 1. Maybe some resolution with the iron gnomes is also missing, because you blow up the Steel Foundry but then they just go chill in their hideout despite all this talk about restoring the status of the ironhand gnomes in BG.
