Well, in this 'harry potter and mom live trunk fanfiction', it could be that they are in the trunk to escape from Voldemort. The trunk might be magically enhanced, like a small but self - contained magical space. They could be using it to hide and plan their next moves. It might also have connections to other magical places, allowing them to get resources or communicate with allies. For example, they could find a way to send messages to Dumbledore through some sort of magical portal in the trunk.
I'm not sure specifically as there could be many different takes in such a fanfiction. It might involve Harry and his mom having some sort of unique adventure while living in a trunk. Maybe they discover a hidden magical world within the trunk or use it as a refuge from the dark forces in the wizarding world.
The 'harry potter and mom live trunk fanfiction' could potentially be about a situation where Harry's mom is brought back to life in some way and they end up living in a trunk. This trunk could be a charmed object that has all the necessities for their survival. It might be filled with magical books that help Harry learn more about his powers and his mother's past. They could be on a journey of self - discovery while in this confined yet magical space. There could be encounters with magical creatures that are also hidden within the trunk's magical environment.