Perhaps the daughter could get into some trouble at school, like accidentally causing a magical mishap during a big exam. Then she has to figure out how to fix it without getting in too much trouble with her mother and the school authorities. It could involve her making new friends who help her out of the situation.
One idea could be that Twilight Sparkle's daughter discovers she has a unique magic ability that even Twilight doesn't fully understand. This could lead to her going on a journey to find out more about it, meeting new characters along the way.
One idea could be that Trixie and Twilight Sparkle team up to solve a mystery in Equestria. Maybe a powerful magical artifact has gone missing and their combined knowledge of magic is needed to find it.
One plot idea could be that Twilight Sparkle and Fluttershy go on an adventure together to discover a new type of magic in Equestria. Along the way, they face challenges that test their friendship and individual strengths.
Well, a great plot could be Twilight Sparkle as an Alicorn going on a journey to discover the origin of Alicorn magic. This could involve her meeting ancient Alicorn spirits and learning secrets about her own powers. Or perhaps she gets caught in a time - loop where she has to repeatedly use her Alicorn powers to break free and figure out what's causing it. It could also be interesting if she has to teach other ponies how to use Alicorn - related magic.
One plot idea could be Twilight Sparkle getting cold feet before the wedding and her friends having to reassure her. Another could be a magical mishap during the ceremony that causes chaos but in the end makes the wedding even more special. Maybe an old enemy tries to disrupt the wedding but Twilight's love for her partner overcomes all obstacles.
One idea could be that the twin sister has a different magical ability. For example, while Twilight Sparkle is good at spells related to knowledge and friendship, her sister could be excellent at magic related to nature. This would create a contrast and also opportunities for them to learn from each other. Another plot could be that the twin sister gets into trouble in a different pony world and Twilight has to go rescue her, leading to all kinds of adventures in unknown places.
One idea could be that the twin brother has a different magical specialty. For example, while Twilight Sparkle is great at magic related to friendship and harmony, her brother could be more attuned to magic of the elements in a different way, like having the power to manipulate natural elements more directly. Maybe he could use his magic to help protect Ponyville from a new, different kind of threat that Twilight's magic isn't as effective against.
One idea could be that Prince Blueblood has to team up with Twilight Sparkle to solve a mystery in Canterlot. Maybe a series of magical artifacts are disappearing and their combined knowledge and skills are needed to figure out who is behind it.
A plot could involve a race between Thomas and one of Twilight's flying friends. Twilight has to referee and make sure it's a fair race. Along the way, they discover that there are some dark forces trying to disrupt the race, and they have to work together to stop them and ensure the race is completed successfully.
One plot idea could be them going on an adventure together to discover a new type of magic in Equestria. Another could be Timber helping Twilight with a difficult spell she's been trying to master.
A plot could involve Flash Sentry and Twilight Sparkle teaming up to organize a magical event in Equestria. However, things go wrong when a jealous pony tries to sabotage their plans. They must then work together to overcome the obstacles, find the culprit, and still make the event a success. This would show their problem - solving skills and how their different personalities complement each other.