Maybe Harry builds a magical trunk that has special compartments for his school supplies, like a self - organizing quill holder and a spell - protected space for his invisibility cloak. It could also have a hidden entrance to a small room where he can study privately without being disturbed by his roommates.
It could be Hagrid. Hagrid is always looking out for Harry and giving him things. He might come across this special trunk during one of his travels in the Forbidden Forest or in some wizarding market and think it would be perfect for Harry.
In the learning trunk, there might be a magical map similar to the Marauder's Map but with more detailed information about the Hogwarts library. It could show hidden sections and the location of books related to specific spells or magical theories. There could also be a set of magical crystals that when held, can transport him into virtual scenarios to practice spells and combat skills in a safe environment.
It's very important. It can be a key element for the plot. For example, if a character discovers a long - lost spell in the trunk, it can change the course of the story.
It can be used to store all kinds of things. For example, a student might use it to keep their school projects safe. One compartment for their potions project, another for their transfiguration assignment.
There could be compartments filled with clothes that magically adjust to the wearer's size and the weather. One compartment might hold a set of invisibility cloaks, and another could have a collection of magical maps. Some compartments could be used to store portraits of important wizards and witches that can communicate and give advice.
Hermione would be a great help. Her vast knowledge of magic and books could provide the necessary information for building the planet, like the right spells and magical theories.
Dumbledore might help in a spiritual or advisory way. Even though he's passed away, his wisdom could be passed on through memories or some magical means. Also, Hagrid could be a great help. He could assist in building areas suitable for magical creatures with his love and understanding of them.
In a fanfiction, Harry Potter could be in a situation where he needs to recruit players with strong muscles for the Quidditch team. He might search through Hogwarts to find students who have been secretly training and have the physical strength required for the tough positions in the game, like the Beaters.