Thank you vux. I downloaded your notes and bookmarks extensions, they are great, thanks for putting in the effort to preserve some of the great old opera features.
I downloaded the Smart RSS one, to bad there is no sidebar version for it yet. Hopefully it will be added in the near future.

In Opera 12.17 you have the elegant efficient and retractable panel which contained my bookmarks, RSS feeds, history, notes and downloads. In my opinion this was what set aside this browser from the rest and made me use that version up until now. But unfortunately, the lack of updating made it incompatible with many website features. I'm reluctantly making the switch to the Opera 31.0 and trying to mimic the old opera functioning.

I have a bar on the left that is similar to the old version one (although not retractable by clicking it), using an extension I added a bookmark menu to it (with an ugly red heart as a symbol). Now I want to add my RSS feeds to it. I downloaded a RSS feed extension, but it did not appear in the bar. Instead it appeared in the upper right corner at the end of the URL bar. I don't know how to move it to the extension bar, can this be done? And do people have tips to mimic the 12.17 panel bar as much as possible?