AFAIK, I don’t think this exists yet.
Not entirely sure if these suit your use case, but Discourse Tooltips and https://meta.discourse.org/t/topic-list-previews/41630/27 are two plugins that do that. They do not limit the view to staff though.
Alternatively, here’s an approach to guide your user: Topic Templates.
However, it does not support defining a topic title template via the settings. Maybe you could include a title convention on the first line to remind the user, or somehow leverage the “prefill by URL” feature (that supports prefilling topic title)?