So you want to have a mode where the non-conflicting changes be not colored?

Please create a sample repository with a conflict on merge/rebase and share your expected output.

You may consider selecting View | Separate Working Tree and Index. Then these files occur in separate lists.

This is supported in the Standard window, "All Branches and Tags" view.

It is called "Reveal Commit".

With rebase, I would say, there would not have been a problem. Maybe it just is my limited understanding, but I don't see any reasonable use-case for merging into a feature branch.

You can configure external tools for that task. Please see https://docs.syntevo.com/SmartGit/Latest/Manual/GUI/Preferences/Tools

This dialog only should come up if the repository has been opened before.

Maybe the translation can be stored in Git notes.