To use Bezier tool inside modeler
Create > Bezier
If you would like to use Bezier tool inside the modeler, you must choose the Bezier option from the Create menu. Bezier allows you to create standard spline curves using tangent controls.
Once you drop the Bezier tool, a normal Modeler curve is created. As such, you cannot re-edit the curve using the Bezier tool.
On the numeric panel, you can create a closed curve and delete the last tangent point.