//Must be on QueuedTask.Run(() => { ...
//Build geometry
Coordinate2D pt1 = new Coordinate2D(3.5, 7.5);
Coordinate2D pt2 = new Coordinate2D(4.16, 8);
Coordinate2D pt3 = new Coordinate2D(4.83, 7.1);
Coordinate2D pt4 = new Coordinate2D(5.5, 7.5);
var bez = new CubicBezierBuilderEx(pt1, pt2, pt3, pt4);
var bezSeg = bez.ToSegment();
Polyline bezPl = PolylineBuilderEx.CreatePolyline(bezSeg, AttributeFlags.AllAttributes);
//Set symbology, create and add element to layout
CIMTextSymbol sym = SymbolFactory.Instance.ConstructTextSymbol(
ColorFactory.Instance.BlackRGB, 24, "Comic Sans MS", "Regular");
var ge = ElementFactory.Instance.CreateTextGraphicElement(
container, TextType.SplinedText, bezPl, sym, "this is the bezier text",
"New Bezier Text", true, new ElementInfo() { Anchor = Anchor.CenterPoint });