public void SetRenderer( 
   CIMRenderer renderer,
   FeatureRendererTarget featureRendererTarget
)

var lyr = MapView.Active.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>().FirstOrDefault(f => f.ShapeType == esriGeometryType.esriGeometryPolygon);
if (lyr == null) return;
QueuedTask.Run(() =>
{
  // GetRenderer from Layer (assumes it is a unique value renderer)
  var uvRenderer = lyr.GetRenderer() as CIMUniqueValueRenderer;
  if (uvRenderer == null) return;
  //layer has STATE_NAME field
  //community sample Data\Admin\AdminSample.aprx
  string expression = "if ($view.scale > 21000000) { return $feature.STATE_NAME } else { return 'All' }";
  CIMExpressionInfo updatedExpressionInfo = new CIMExpressionInfo
  {
    Expression = expression,
    Title = "Custom" // can be any string used for UI purpose.
  };
  //set the renderer's expression
  uvRenderer.ValueExpressionInfo = updatedExpressionInfo;

  //SetRenderer on Layer
  lyr.SetRenderer(uvRenderer);
});

var lyr = MapView.Active.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>().FirstOrDefault(f => f.ShapeType == esriGeometryType.esriGeometryPolygon);
if (lyr == null) return;
QueuedTask.Run(() =>
{
  //Get the layer's definition
  //community sample Data\Admin\AdminSample.aprx
  var lyrDefn = lyr.GetDefinition() as CIMFeatureLayer;
  if (lyrDefn == null) return;
  //Get the label classes - we need the first one
  var listLabelClasses = lyrDefn.LabelClasses.ToList();
  var theLabelClass = listLabelClasses.FirstOrDefault();
  //set the label class Expression to use the Arcade expression
  theLabelClass.Expression = "return $feature.STATE_NAME + TextFormatting.NewLine + $feature.POP2000;";
  //Set the label definition back to the layer.
  lyr.SetDefinition(lyrDefn);
});

//The layer must be track aware and spatial
if (streamLayer.TrackType != TrackType.Spatial)
  return;
//Must be on QueuedTask!
//Define unique value classes same as we do for current observations
//or use "CreateRenderer(...)" to assign them automatically
CIMUniqueValueClass uvcB727Prev = new CIMUniqueValueClass()
{
  Values = new CIMUniqueValue[] { new CIMUniqueValue() {
    FieldValues = new string[] { "B727" } } },
  Visible = true,
  Label = "Boeing 727",
  Symbol = SymbolFactory.Instance.ConstructPointSymbol(
    CIMColor.CreateRGBColor(255, 0, 0), 4, SimpleMarkerStyle.Hexagon)
    .MakeSymbolReference()
};

CIMUniqueValueClass uvcD9Prev = new CIMUniqueValueClass()
{
  Values = new CIMUniqueValue[] { new CIMUniqueValue() {
    FieldValues = new string[] { "DC9" } } },
  Visible = true,
  Label = "DC 9",
  Symbol = SymbolFactory.Instance.ConstructPointSymbol(
    CIMColor.CreateRGBColor(0, 255, 0), 4, SimpleMarkerStyle.Hexagon)
    .MakeSymbolReference()
};

CIMUniqueValueGroup uvGrpPrev = new CIMUniqueValueGroup()
{
  Classes = new CIMUniqueValueClass[] { uvcB727Prev, uvcD9Prev }
};

var UVrndrPrev = new CIMUniqueValueRenderer()
{
  Fields = new string[] { "ACTYPE" },
  Groups = new CIMUniqueValueGroup[] { uvGrpPrev },
  UseDefaultSymbol = true,
  DefaultLabel = "Others",
  DefaultSymbol = SymbolFactory.Instance.ConstructPointSymbol(
    CIMColor.CreateRGBColor(185, 185, 185), 4, SimpleMarkerStyle.Hexagon)
    .MakeSymbolReference()
};
        
streamLayer.SetRenderer(UVrndr, FeatureRendererTarget.PreviousObservations);

//The layer must be track aware and spatial
if (streamLayer.TrackType != TrackType.Spatial)
  return;
//Must be on QueuedTask!
//Note: only a simple renderer with solid line symbol is supported for track 
//line renderer
var trackRenderer = new SimpleRendererDefinition()
{
  SymbolTemplate = SymbolFactory.Instance.ConstructLineSymbol(
      ColorFactory.Instance.BlueRGB, 2, SimpleLineStyle.Solid)
        .MakeSymbolReference()
};
streamLayer.SetRenderer(
     streamLayer.CreateRenderer(trackRenderer), 
       FeatureRendererTarget.TrackLines);