I've been playing around with splitView for a few days now, and it's in an excellent state for a brand new feature, but there are some friction points that could do with some quality of life massages to really shine as a browser feature.
Say you have tabs A and B, and you put them into Split View A|B. Later, you decide A|B isn't working for your workflow, and you want to try B|A. It is a 5-6 click process to swap from A|B to B|A.
The friction could be entirely reduced with the addition of a single 'swap view' button that simple changes between A|B and B|A when pressed.