This thought just occurred to me as I glanced over a notification that came in on another thread ("...there does not seem to be a way of seeing exactly which layout is in action for a page, even by inspecting the code." Source)
What about a new little icon in the admin menu that either links to a separate page or has a little dropdown info pane with details about the current page you are viewing?

For example, all in one place, info (and potentially links to edit/adjust) about the:
- Layout used on this page
- Theme
- Content type
- etc.
That may be overkill but thought I'd throw it out there to see what people thought.
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