Final answer:
Madison should click the plus sign to add a new element to her 2D screen in the hierarchy, commonly found in game development environments.
Step-by-step explanation:
If Madison is ready to customize her game title and has clicked on her 2D screen within the hierarchy, the next step to add a new element would typically be to click the plus sign. In most software used for game development or graphics editing, a plus sign is often used to add new elements to the workspace or scene. For instance, if she is using a game development environment like Unity, she would look for the plus sign to add a new UI element, sprite, or other game objects.