TChartLegend.Placement Property
Placement of the legend inside of the chart. Note that newer Excel versions might report a non docked placement even if the legend is docked to a side. You need to check CanOverlapWithChart to see if the legend is docked, and then look at the side it is to see if it is docked to the left, top, etc.
Syntax
Namespace: FlexCel.Core
public TChartLegendPlacement Placement { get; set; }