Hello. I just started using Opera recently and I really like it. I am primarily a Firefox user, so obviously I am requesting the best features Firefox has to be implemented into Opera so that I can switch over fully.
Give users the option to move the sidebar to the right side.
With the sidebar on the right side, then that means the bookmarks are on the right side as well.
Opera has "show bookmarks bar", which is the top part under the address bar, and "show sidebar". Allow the option to "show bookmarks sidebar".
Bonus: Allow the option to add a search bar next to the address bar. Some people like their search bar separate from their address bar.
I'm sure people have asked for this before, but you haven't added it yet so I am making this to let you know there is demand for it.