[GitaraMoya]

great extension but is it made by Opera?

No but all extensions posted in the repository are checked, so they don't contain any harmful code or any tracking without the user's consent.

By the way one feature I like is the bookmark nickname feature : for each bookmark you can assign a nickname to it; eg if you have sunniforum as a bookmark, right click on it, properties and in nickname type s. This work for any bookmark so it becomes handy to open many bookmarks rapidly.