(Leaflet cofounder here) - sorry about that! Are you seeing that with 'canvas' pages, or multiple doc pages open side by side? What device / screen size? I haven't seen issues with horizontal scroll recently but lots of trickiness with slight differences across browsers and maybe things we can improve for particular cases.

Re: scrollbars honestly we just like the cleaner minimalist look and have gotten used to it but I hear you (+ others) that it can be annoying, we'll look into improving.