public static bool CanAppendToLinkChart( 
   Map linkChart,
   KnowledgeGraphLayerIDSet idSet
)

{
  //We create an id set to contain the records to be appended
  var dict = new Dictionary<string, List<long>>();
  dict["Suspects"] = new List<long>();

  //In this case, via results from a query...
  var qry2 = "MATCH (s:Suspects) RETURN s";

  await QueuedTask.Run(async () =>
  {
    using (var kg_for_lc = kgLayer.GetDatastore())
    {
      var graphQuery = new KnowledgeGraphQueryFilter()
      {
        QueryText = qry2
      };

      using (var kg_rc = kg_for_lc.SubmitQuery(graphQuery))
      {
        while (await kg_rc.WaitForRowsAsync())
        {
          while (kg_rc.MoveNext())
          {
            using (var graphRow = kg_rc.Current)
            {
              var obj_val = graphRow[0] as KnowledgeGraphNamedObjectValue;
              var oid = (long)obj_val.GetObjectID();
              dict["Suspects"].Add(oid);
            }
          }
        }
      }

      //make an ID Set to append to the LinkChart
      var idSet = KnowledgeGraphLayerIDSet.FromDictionary(kg_for_lc, dict);
      //Get the relevant link chart to which records will be
      //appended...in this case, from an open map pane in the
      //Pro application...
      var mapPanes = FrameworkApplication.Panes.OfType<IMapPane>().ToList();
      var mapPane = mapPanes.First(
        mp => mp.MapView.IsLinkChartView &&
        mp.MapView.Map.Name == "Acme Link Chart");
      var linkChartMap = mapPane.MapView.Map;

      //or get the link chart from an item in the catalog...etc.,etc.
      //var projectItem = Project.Current.GetItems<MapProjectItem>()
      //      .FirstOrDefault(pi => pi.Name == "Acme Link Chart");
      //var linkChartMap = projectItem?.GetMap();

      //Call AppendToLinkChart with the id set
      if (linkChartMap.CanAppendToLinkChart(idSet))
        linkChartMap.AppendToLinkChart(idSet);
    }
  });
}

{
  //using ArcGIS.Core.Data.Knowledge.Extensions;

  var linkChartView = MapView.Active;

  await QueuedTask.Run(async () =>
  {
    var ffp_config = new CIMFilteredFindPathsConfiguration();
    ffp_config.Name = "Append to Link Chart from FFP Results";
    //set up config
    //...

    var results = kg.RunFilteredFindPaths(ffp_config);

    var pathsEntitiesAndRelationships = results.ExtractPathsEntitiesAndRelationships(null);

    //Create a KG layer id set
    var kgLayerIdSet = KnowledgeGraphLayerIDSet.FromKnowledgeGraphIDSet(
      pathsEntitiesAndRelationships.ToKnowledgeGraphIDSet(
        KGResultContentFromFFP.EntitiesAndRelationships));

    var map = linkChartView.Map;

    if (!map.CanAppendToLinkChart(kgLayerIdSet))
      return;//not compatible

    map.AppendToLinkChart(kgLayerIdSet);
    //switch layout algo
    var algo = linkChartView.GetLinkChartLayout();
    if (algo != KnowledgeLinkChartLayoutAlgorithm.Hierarchical_TopToBottom)
    {
      //Change layout algo to match the default used by the UI after FFP
      await linkChartView.SetLinkChartLayoutAsync(
        KnowledgeLinkChartLayoutAlgorithm.Hierarchical_TopToBottom);
    }

    //To set link chart root nodes see 'Create Link Chart from FFP Results'
  });
}