It would be nice to have an extra, optional field when modeling content to provide a more detailed description of the field or some basic instructions for the content creator.
Currently we use the placeholder field to try to relay extra information but often it is not enough space or just not the best fit.
If a field could have a description, that would make the content model self-documenting from developers to content authors.
Currently, we maintain separate documentation that contains specifics of fields, which requires extra work. For example, if a field is optional, we document how that impacts the content. Other examples can be specifying file types or specific dimensions for image fields, or noting a character limit for copy.
By having a description field, all the documentation would live directly in the model.
Edit: Along this same line, having a notes field that was admin-only would also be nice to put at the top of the document. This could be used to provide general information about all the fields.
I made a quick mockup to give an idea what I'm taking about: