Problem solved! I never right clicked on the scene list before. "Clone selected scene(s)" already exists there. Doesn't in the Scene menu.
(I should stop giving context as it always misleads and never is relevant; in this case I was 100% sure the option wasn't in yWriter and wanted to elaborate so writers with similar needs would comment!)
Peter:
only the viewpoint character is adopted in the newly created scenes; the remaining relationships must be re-created manually.
When I tried that option, it did copy the locations as well. What do you mean by "remaining relationships"? Isn't mono-POV the only thing you can do about characters in a scene?
Peter & Christian:
Does that mean that your 10000-word scenes take place in a lot of locations with a lot of characters? Then perhaps we don't quite have the same understanding of what constitutes a scene.
I think we do! A scene is same place/same characters.
Some discussions need more words than others. That's my benefit, Christian! Words that have a meaning for the story.
To be fair, my latest long scene was technically several scenes, because some random characters appear. However, I don't even mention all my secondary characters in yWriter (scrolling already is long), so I never take time to add a character that will be present for half a chapter out of 200, and add/remove them in scenes of that chapter (multiply the work by all such random NPCs across the novel - I'd rather be writing). Hence me saying it's a single yWriter scene: only 2 characters are constantly registered, so cloning the scene would have been extremely effective.
Many thanks for your help!