An option during split-screen to allow the user to choose the orientation of split-screen i.e. either side-to-side or top-down.
Currently, it is only possible to split screen side-to-side and it is really not helpful when you have a vertical monitor, or when you want split screen functionality when you size your browser to just one half of your screen
This is a feature I've seen in Microsoft Edge but there is no option as far as I'm aware on both Opera and Opera GX. And it allows us to do something like this
(example)
Opera already has a 3 dot menu between split screen but it only allows to either exit split screen or rate it. Adding the option to choose orientation there feels like the logical step.