@leocg Ah thats sad news.
This is a very apprechated feature on the Arc Browser and on Samsung devices. Hope Opera can implement it as well, I use Split screen on soo many website combos daily.

How do save a split screen setup for two websites?
All I can find is save them as a separate bookmarks in a folder on the start page. However there is many steps to get them back as a split screen. I want a quick single bookmarkbutton in the bookmark bar....

Absolute fantastic! Thank you!