Cool! This could be interesting as the base for a quick kanban board for mid-sized personal projects.
That said: agree with others that sharing state between devices (either yours or others), and being able to collaborate on the same board, is sort of the canonical feature requirement of kanban boards. They can be used for 1-person projects, goal tracking, etc. - I've used e.g. Notion boards in this way - but they gain most of their value from allowing multiple people to share awareness of task status and ownership.
Plus the use of localStorage means I'd eventually blow away my board state by accident - which is kind of a showstopper IMHO; being able to trust your tools is important.
Still: nice to see people experimenting with what you can do just using web basics :)