[fransje26]

If I understood your point correctly, I believe that Meld can do that. And then you get a windows as [1]. You can configure git to choose which version goes where. Something like:

    [mergetool "meld"]                                                                                  
        cmd = meld "$LOCAL" "$MERGED" "$REMOTE" --output "$MERGED"                                      
        #cmd = meld "$LOCAL" "$BASE" "$REMOTE" --output "$MERGED"

[1] https://linuxkamarada.com/files/2019/11/git-mergetool-meld-e...