public bool IsEditable {get;}

var featSceneLayer = MapView.Active.Map.GetLayersAsFlattenedList()
                   .OfType<FeatureSceneLayer>().FirstOrDefault();
if (!featSceneLayer.HasAssociatedFeatureService || 
    !featSceneLayer.IsEditable)
  return;//not supported

//TODO continue editing here...

//must support editing!
//var featSceneLayer = ... ;
if (!featSceneLayer.HasAssociatedFeatureService || 
    !featSceneLayer.IsEditable)
  return;
//Check geometry type...must be point in this example
if (featSceneLayer.ShapeType != esriGeometryType.esriGeometryPoint)
  return;

var editOp = new EditOperation()
{
  Name = "Create new 3d point feature",
  SelectNewFeatures = true
};

var attributes = new Dictionary<string, object>();
//mapPoint contains the new 3d point location
attributes.Add("SHAPE", mapPoint);
attributes.Add("TreeID", "1");
editOp.Create(featSceneLayer, attributes);
editOp.ExecuteAsync();//fyi, no await

//must support editing!
//var featSceneLayer = .... ;
if (!featSceneLayer.HasAssociatedFeatureService || 
    !featSceneLayer.IsEditable)
  return;

var delOp = new EditOperation()
{
  Name = "Delete selected features"
};
//Assuming we have a selection on the layer...
delOp.Delete(featSceneLayer, featSceneLayer.GetSelection().GetObjectIDs());
await delOp.ExecuteAsync();//await if needed but not required

//must support editing!
var featSceneLayer = MapView.Active.Map.GetLayersAsFlattenedList()
                   .OfType<FeatureSceneLayer>().FirstOrDefault();
if (!featSceneLayer.HasAssociatedFeatureService || 
    !featSceneLayer.IsEditable)
  return;

var ok = await QueuedTask.Run(() =>
{
  var editOp = new EditOperation()
  {
    Name = "Edit FeatureSceneLayer Attributes",
    SelectModifiedFeatures = true
  };
  //make an inspector
  var inspector = new Inspector();
  //get the attributes for the specified oid
  inspector.Load(featSceneLayer, oid);
  inspector["PermitNotes"] = "test";//modify
  editOp.Modify(inspector);
  return editOp.Execute();//synchronous flavor
});