How to increase or decrease control points
Left-Click on the “Free Curve” icon to enter the command of drawing line.
◆ Add new curve control point:Left mouse click on the Viewport.
◆ Add a duplicate curve point:Left button Double-click on the same control point, a duplicate point will be added.
◆ Delete point:Hold down the Left button and click the right button to delete control points
“Spacebar” to end the command

How to edit the curve again
Right-Click on the icon and select curve to edit

The Role of Command Line Options for Drawing
◆Curve Color:Changes the color when drawing and creating curves.(Hotkeys: A + Spacebar)

◆ Ortho:Open ortho mode can draw straight line(Hotkeys: S + Spacebar)

◆Close:Closes the open curves.(Hotkeys:D + Spacebar)

◆ Thickness:The thickness of the curve, Default value is 2, usually do not modify(Hotkeys: V + Spacebar)

Advanced operations(Premise:Open Object axis)
◆ Hold down Ctrl + left mouse button and click on the Viewport to Draw a new curve.
◆ Hold down Shift + left mouse button and click other curves to Edit other curves.

Video Tutorials
◆ If you want to learn by video, click on the link below to jump to Youtube