Thanks Rainer. Selection to Background has its uses, but as far as I know only keeps one copy, whereas I like to keep a breadcrumb trail of significant edits in case I have to backtrack. it's handy that I can rename them too. And it's very easy to delete redundant layers.
I assumed that a simple script would be the answer, so now I just have to find out how to write it. A Keyboard Maestro click shortcut is doing it for me until I have the time for that. It does still seem an obvious candidate for a native menu item/shortcut.