I think the todo list has a lot of potential, but I don't see it very useful as is. Two ideas that I think can make it much more robust:
1. Have a global todo list view. So you can view all of the todo items from across all of your todo lists. And you can easily go complete them from this view and easily see where each todo item is from.
2. When creating a todo in the body of your note, this todo is automatically added to your todo list. This is the same exact item, but viewed in 2 different places (3 if you include the global list). So when you update this todo item from the note or from the list (or from the global list), then it updates it across all views since it's one item.