Maybe Harry realizes he made some mistakes in his past and decides to go back in time to correct them. He could try to save his loved ones who died in the original story.
In this fanfic, Harry might use his knowledge of the future to avoid certain dangerous situations. He could also work on improving the wizarding world from an earlier stage, like trying to make Hogwarts a more inclusive place right from the start.
It could be that Harry wants to change his relationships. For example, he might try to befriend some people he had misunderstandings with before. He could also focus on his studies more and become an even better wizard earlier in his new life.
Voldemort would still be a crucial character. Since Harry is redoing his life, he might try to defeat Voldemort in a more strategic and less dangerous way. Other characters like the Weasley family, who were always there for Harry, would be involved too. They could be part of Harry's new support system in his redone life.
One interesting plotline could be Harry using his knowledge from his first life to prevent certain tragedies. For example, he might be able to save Sirius Black much earlier by being more cautious about the events at the Ministry of Magic. Another could be him changing his relationships with his classmates. He might befriend Draco Malfoy in a different way, perhaps by reaching out to him and understanding his family situation better, which could lead to a very different dynamic at Hogwarts.
Perhaps Harry is given the task of mentoring some young Ravenclaw students. As he spends time with them, he starts to appreciate the values of Ravenclaw more. He might learn from them as much as he teaches them, and this could lead to new friendships and a different perspective on the Hogwarts houses in general. Along the way, they could face challenges together, like dealing with a new dark magic threat that targets Ravenclaw specifically.
Maybe Harry is a thief to steal back something important that was taken from him or his family. For example, a magical heirloom that has been wrongfully confiscated.
Maybe Harry becomes an assistant to the doctor and they go on adventures through time and space. They might encounter various alien species and solve mysteries together.
One possible plot could be that Harry and Kara are in a relationship. When Kara discovers she's pregnant, they face challenges together. Maybe they have to deal with the reactions of their friends and family, and they struggle to balance their own dreams and the upcoming arrival of the baby. For example, Harry might be on the verge of a big career opportunity, but he has to put it on hold to support Kara during her pregnancy.
One possible plot could be that Harry Potter, through some magical mishap or powerful spell, is transformed into a bride. Maybe he has to go on a quest to find a way to reverse the spell while dealing with the strange reactions of his friends and the wizarding world. For example, Ron might be completely confused and Hermione would be trying to find a solution in the library.
Perhaps Harry sues the Weasleys because he believes they misused some of his fame for their own financial gain. For example, they might have used his name to promote their joke shop without his permission. And Harry, being fed up with this exploitation, decides to sue them to set things straight.
It could be that Ginny uses a dark magic spell in a moment of anger or recklessness. Harry, being the defender of the light, punishes her by making her study the history of the harm caused by dark magic. As she delves into this study, she realizes the error of her ways and has to work hard to regain Harry's trust. This could involve her doing community service within the wizarding community related to those who have been affected by dark magic.
A plot twist might be that the goblins turn against Harry midway through his visit. They could be influenced by a dark wizard who has a grudge against Harry. This would completely change the course of his visit and force him to find a new way to achieve his goals in Gringotts. Another possibility is that the vault contains a magical item that has a mind of its own and tries to possess Harry when he touches it.