@leocg thanks, but it's something else.
When I have set Opera as my default browser in Android, when opening a link in another application (e.g. Feedly RSS reader) I'd like it to load a page in the background, but do not leave the original application. Then a loaded page could be accessed through a notification (which would activate and open Opera) or using a bubble (draw a floating bubble over other apps). The former is how Firefox implemented it, and the latter is Lynket browser solution to the problem (feature is called Web Heads).