"Confirm copy on double-click operation" always disabled

The option "Confirm copy on double-click operation" in the Double-click section of "Panels" in the preferences does not enable even when the selected operation is "Copy". I havevn't found any way to enable this option.

I'm on 5.7.6 (Build 5874) and "Check for updates" says that I'm current.

Am I doing something wrong, or is this a bug?

You have to enable generic [i]Transferring of files[/m] confirmation:
https://winscp.net/eng/docs/ui_pref_environment

I've updated the documentation to make this clear.
https://winscp.net/eng/docs/ui_pref_panels#double-click