5.1. Smooth  S

Gently smooth out a curve.

5.2. Smooth More  Ctrl+S

Strong smooth effect on a curve.

5.3. Clone

Make a clone of this curve in place. You will need to move the new curve away from the original to see them separately.

5.4. Mirror Clone

Duplicates and mirrors the new curve.

Whereas "M" symmetry creates a virtual fourth line for a lathe object, Mirror Clone can be used to create a real fourth line opposite the third, and since this avoids using symmetry the map can be different on either side of the model.

5.5. Redraw As...

Redraws an entire curve to fit a precise shape.
To make accurate geometric curves and perfect spheres and ellipses use these commands to turn rough shapes into exact curves. Redraw As... Semi-Circle is especially useful for making spheres, Redraw As... Straight-Line helps make flat planes out of loft objects.

5.6. Ruler Mode...

Sets the style of the Straighten Curve Segment (Ruler) tool.
Drag over a portion of a curve to redraw it in the chosen style.

5.7. Draw Smooth Lines

By default curvy applies heavy smoothing to each drawn curve.

5.8. Draw Precise Lines

Choose this option to allow raw unsmoothed curve drawing.