Strange… I usually put my index finger on scroll wheel when I need to scroll, so right button+scroll feels way more natural. Maybe this could be investigated further.
Or - yeah - add an option. But I'm telling you: I'm pretty sure that a lot of people use index finger to scroll with the wheel, not the middle one.
Maybe off-topic but I tried to copy Current Session -file from Opera developer to Vivaldi and it kind of worked but restored just one of my 3 windows in that session. (Import from Opera 15.x should allow import also from beta/developer versions because those users (I included) are potential switchers.
This build's install (update) ran on and on (twice), so I had to manually stop it. But when I tried the last build, it turns out to have actually installed.
I note that it still opens to the last seen page. What's the point of a home page?