Update an existing Calibre entry with a new file

It's possible there's a good way to do this and I simply missed it.

Places like Project Gutenberg tend to issue newer versions of existing titles, with better proofreading and other detail fixes. Add Books will produce a dialog stating the book is a duplicate of an existing entry. I need to accept the duplicate, then perform surgery.

What I'd like is an update option to say "Replace the existing eBook file with this version, but keep the existing metadata."

Is there something I've missed that addresses this, or am I making a feature request?

Thanks,
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Dennis