As a publisher, I want to be able to provide a brief prose description of the content and meaning of each map layer in the table of contents. NOT technical metadata or REST service definition, such as that currently presented by the Description command under the ellipsis (...) in the table of contents.
Analogous to the "About" widget at the app level of WebAppBuilder, but this would be for each layer. It would be the duty of the publisher to supply the content, just as they do now for "About" the app.
Yes, story maps are designed to do this sort of thing, but they are not appropriate in every circumstance.