You can edit a curve's control points to get to more rich and complicated curves.
You can edit the control points from any camera angle. You can also use the control point's axis handlers to move them more accurately on their axis.
To add more control points:
Press & Hold on the curve's path, then a tooltip will appear - tap on "Add".
To delete a control point:
Press & Hold on an existing control point and tap "Delete".
To merge control points:
Drag curve's edges (their circles are marked in Green). Once you drag one on top of another, a tooltip will appear - you can select from 3 different options:
Connect - will connect the dots and will close the shape
Merge - will merge the two points to one point
Blend - will merge the two points and create a smooth connection