davehawley: On this page I just have a grey star at the right-hand end (and a yellow padlock off the Left-hand end).
When I right click in a page I get a dialog with Bookmark Page... This gives me the Add Bookmark dialog - with nothing about thumbnails. I usually right click on my required folder in the Bookmarks column to get the Add Bookmarks dialog.
Could there be something in Tools/Preferences/Advanced/Tabs. Thumbnails are mentioned but I don't see the relevance?
vux777: My Opera version is:
About Opera from Help
System Windows 7