public void SetFilters( 
   IEnumerable<CIMPointCloudFilter> filters
)

{
  // Note: call within QueuedTask.Run()
  {
    //Retrieve the available classification codes
    var dict = pointCloudSceneLayer.GetAvailableClassCodesAndLabels();

    //Filter out low noise and unclassified (7 and 1 respectively)
    //consult https://pro.arcgis.com/en/pro-app/help/data/las-dataset/storing-lidar-data.htm
    var filterDef = new PointCloudFilterDefinition()
    {
      ClassCodes = dict.Keys.Where(c => c != 7 && c != 1).ToList(),
      ReturnValues = new List<PointCloudReturnType> {
                        PointCloudReturnType.FirstOfMany }
    };
    //apply the filter
    pointCloudSceneLayer.SetFilters(filterDef.ToCIM());
  }
}

{
  // Note: call within QueuedTask.Run()
  {
    var filters = pointCloudSceneLayer.GetFilters();
    PointCloudFilterDefinition fdef = null;
    if (filters.Count() == 0)
    {
      fdef = new PointCloudFilterDefinition()
      {
        //7 is "edge of flight line" - exclude
        ClassFlags = new List<ClassFlag> {
         new ClassFlag(7, ClassFlagOption.Exclude) }
      };
    }
    else
    {
      fdef = PointCloudFilterDefinition.FromCIM(filters);
      //keep any include or ignore class flags
      var keep = fdef.ClassFlags.Where(
             cf => cf.ClassFlagOption != ClassFlagOption.Exclude).ToList();
      //7 is "edge of flight line" - exclude
      keep.Add(new ClassFlag(7, ClassFlagOption.Exclude));
      fdef.ClassFlags = keep;
    }
    //apply
    pointCloudSceneLayer.SetFilters(fdef.ToCIM());
  }
}