Currently, displaying a request+response pair side-by-side is only possible in Repeater ("Repeater -> View -> Left/right split" from the menu bar) or via extensions like Flow or Logger++. I use this layout a lot and I'd like to have it in other areas of Burp Suite, like Target / Site Map, Proxy / History, Intruder results, ...
We have this logged in our development backlog. Unfortunately, we can’t provide an ETA.
Having side-by-side panes in history is handy for quick manual "intruder"-like checks and taking docing screenshots.