There are two different functionalities being described here. One is the default (or optional) opening method when clicking a link, and the other is hosting two side-by-side views that are independent of each other.
For the former I did a writeup describing how elegantly Superlist solves this problem (way more functional than obsidian’s sliding panes) as a comment on this other feature request. Regarding the latter, agreed it’s an excellent, helpful, but separate capability that should be considered.