pi@retropie:~/.attract $ testvar=$(grep -A 1 ^display attract.bak | grep -iv kodi | tail -n1)
pi@retropie:~/.attract $ echo "$testvar"
    layout               unified
pi@retropie:~/.attract $ newvar="        layout               testdisplay"
pi@retropie:~/.attract $ echo "$newvar"
        layout               testdisplay
pi@retropie:~/.attract $ sed -e "s/$testvar/$newvar/g" "attract.bak" | grep [[:blank:]]layout[[:blank:]]
        layout               testdisplay
        layout               testdisplay-favorites
    layout               kodi
        layout               testdisplay
        layout               testdisplay
        layout               testdisplay
        layout               testdisplay
        layout               testdisplay
        layout               testdisplay
        layout               testdisplay
        layout               testdisplay
        layout               testdisplay
        layout               testdisplay
        layout               testdisplay