Seconding the use of p4merge for easy-to-use three-pane merging. Just like most other issues with Git, if your merges are painful it's probably due to terrible native UX design - not due to anything conceptually wrong with Git.
I also use the merge tool of JetBrains IDEs such as IntelliJ IDEA (https://www.jetbrains.com/help/idea/resolve-conflicts.html#r...) when working in those IDEs. It uses a three-pane view, not a four-pane view, but there is a menu that allows you to easily open a comparison between any two of the four versions of the file in a new window, so I find it similarly efficient.
https://github.com/microsoft/vscode/issues/155277#issuecomme...
No matter the tool, merges should always be presented like that. It's the only presentation that makes sense.
Addendum: I've since long disabled it. A and B changes are enough for me, especially as I rebase instead of merging.