Once in the Magit buffer, hit E, choose the diff and when they're displayed then switch to vertical mode with |.
So far so good.
However, this shows three panes, not two.
- How to show just current and last commit?
- How to make both document linked while scrolling? At the moment one of them can have collapsed headings while the other does not, and it's impossible to see.
- How to only show changes (not all document) like in Github, for instance, where it only shows changes and some lines before and after?
d dmight be the answer to point 3, also you can expand
TAB and presse` on any of the commits. which might be the answer to point 1).