Cannot Add Buttons
Virtually the entire Operawiki applies to Opera version 12.17 and older - the "Presto"-engined Opera versions. After Opera was completely redesigned at version 15, the customizations of those old versions no longer apply nor work for the new version. Operawiki (and other old-sourced) buttons fall into that category... they only work on the old versions. The new versions of Opera are considerably simplified, compared with the older versions. Instead of the native customization capability of the old version, interface customizations (where they even exist) for the new versions usually need to be made using various extensions.
The Operawiki really needs to be edited to prominently indicate it only applies to the old Presto Opera versions... there's already enough confusion surrounding the two families of Opera browsers.
Dang that really sux. One of the things I loved about Opera was that it could be customised.
Seems like everything is being dumbed-down these days.
You can use Opera 12. What is the problem? Opera 12 is still supported by Opera.