I think it would be cool if you could configure bookmarks to either keep or automathically delete search history while using that particular bookmark.
This would be an helpful addition to Opera, because when you search stuff in incognito mode you are always asked to accept cookies or login while entering basically every website, whereas if you had sought stuff in a normal bookmark you would have no reason to do that for websites you have already visited (assuming that you saved your credential in those sites).
That would be the convenience of a bookmark in which you could look up temporary stuff that would not be counted in your search history.