Hi Alex,
The control over the automatic legend items is limited to changing the order in which they are added (through the series.Legend.Order property). If you need better control, you can use the legend in "manual" mode. The following code demonstrates how to add a legend item in this mode.
NLegend legend = nChartControl1.Legends[0];
legend.Mode = LegendMode.Manual;
NLegendItemCellData item0 = new NLegendItemCellData();
item0.Text = "Custom item";
item0.TextStyle.FontStyle = new NFontStyle("Arial", 9);
item0.MarkLineStyle = new NStrokeStyle(0, Color.Black);
item0.MarkBorderStyle = new NStrokeStyle(1, Color.Black);
item0.MarkFillStyle = new NColorFillStyle(Color.Red);
item0.MarkShape = LegendMarkShape.Rectangle;
legend.Data.Items.Add(item0);
Best Regards,
Nevron Support Team