The 'absolute' mode enables copy and paste. But 'enable copy' mode doesn't (on one of the sites I usually visit). The developer explains here https://github.com/ssborbis/ContextSearch-web-ext/issues/95 that the 'Absolute Mode' simply removes all event listeners of type. It seems the site I was looking to make this work was a bit more aggressive. FYI - on the same site drag and copy works with just the 'enable copy' mode. Thanks to the developer for a useful addon.