I have to start with saying that I'm really in love with the opera browser. It is the best one I have tried so far. But I'd like to see a view new features. Not because I think it will make Opera so much better. But because I'd really like to see these features.
Every time I visit a website, the site asks for the permission to show notifications. Since I disabled cookies the settings aren't saved. With time it gets really annoying if it's asking you like 50 times a day. So I'd like a feature that disables that.
I know it sound kinda useless but I'd like to have some kind of toolbox in the sidebar. Where, when you open it, different features appear. Like a calculator or so, translator or so. But that one would really be the bees knee. So not to important.
And last and probably least . I'd like some designs for the sidebar or the one on the top. If you don't know what I mean, have a look at the browser called "Naver Whale".
Other than that the browser seems to be pretty perfect.