How does the metadata editor indicate that information is missing?

The metadata editor indicates that information is missing through prompts at the top of the page, directing users to the specific missing pieces. This feature is designed to enhance user experience by providing clear guidance on what is required for each section of the metadata. By placing the prompts at the top, the editor ensures that users can easily notice and address the omissions before proceeding, thus maintaining the integrity and completeness of the metadata entry process. This approach is particularly beneficial in complex datasets where clarity in data management is crucial.

In contrast, the other options do not serve as primary indicators for missing information in the same direct and user-friendly manner. While some may involve visual cues or additional prompts, they do not effectively target user attention like the prompts at the top of the page do. This makes the correct answer a more efficient choice for guiding users in filling out metadata completely.