Never in a million years would I want the code going left to right. Once you account for all of the toolbars and everything else that Studio has, even on a widescreen it doesn't have that much horizontal space. As Ricardo says, scroll wheels go vertically. Scaffolding does stuff vertically too, not that it is the final determination of truth, but why rearrange everything the system does?
And really? Left to right vs. top to bottom doesn't matter too much if the action is small enough to fit on one screen. As soon as it does get bigger than the screen, top-down is simply easier for a bunch of arbitrary reasons that we can't change.
Finally, once you upgrade to a proper 4k monitor of any decent size, you quickly find out that a really great way to work is to snap Studio to one side of the screen and the browser to the other side, so you can test, have your user stories, etc. side by side with Studio, and once you do that, you Studio has a lot more vertical space and a lot less horizontal space.
Bottom line: OutSystems made the change for False to be down a long time ago, it was the wrong decision, we've been complaining about it for years (close to 10 years now), people who never knew the old, "right" way know the current way is wrong, and this is likely a 5 second change, and OutSystems still won't change it. Don't know why.
J.Ja