I think there should be a option to add a website to the sidebar and just access them in just a blink instead of the limited options we have. People doesn't just only want the limited options. And plus it helps multitasking.
What to put:
In the sidebar with the plus button it will show a website what to show.
maybe you want to put google.com in the side and search while in your current webpage in opera. You can search for the website and click the website to put to the sidebar and it will show as an icon (or just put the recommended websites or put a link)
and now you have google in the sidebar, click it and it will open but it will block some parts of the webpage while surfing, some people might not want this so then add the option to PIN the side website and it will adjust the website your on to the side.