dndoff.scpt

if ! [[ $(plutil -convert xml1 -o - ~/Library/Preferences/ByHost/com.apple.notificationcenterui.*.plist | grep false) ]]; then
    osascript <<EOD
      tell application "System Events" to tell process "SystemUIServer"
        key down option
        click menu bar item 1 of menu bar 1
        key up option
      end tell
EOD
fi

dndon.scpt

if [[ $(plutil -convert xml1 -o - ~/Library/Preferences/ByHost/com.apple.notificationcenterui.*.plist | grep false) ]]; then
    osascript <<EOD
      tell application "System Events" to tell process "SystemUIServer"
        key down option
        click menu bar item 1 of menu bar 1
        key up option
      end tell
EOD
fi

Does this work for you in Mojave? I can't get it to option-click the Notification Center icon; it just registers as a standard click.