isVisibleInLegend property
Show/hides the legend for trendline.
Defaults to true.
Widget build(BuildContext context) {
  return SfCartesianChart(
    series: <CartesianSeries<ChartData,String>>[
      LineSeries<ChartData,String>(
        trendlines: <Trendline>[
          Trendline(isVisibleInLegend: false)
        ]
      )
    ]
  );
}
Implementation
final bool isVisibleInLegend;