Joining paths

To combine two open paths into a single path, select the paths, and then click Join Path on the Object menu (or press CTRL+J). Expression Design moves the two end anchor points that are closest to each other to a position halfway between the two objects.

The original paths (top) and after clicking on Join Path (bottom)

Joining with the drawing tools

You can also join two paths with the various drawing tools, as long as the Drawing tools append to path check box is enabled in the Stroke panel of the Options dialog box. With the Line, Pen, Polyline, or B-Spline tools, start drawing over the beginning or ending anchor point of the first path, and finish drawing over the beginning or ending anchor point of the second path. With the Paintbrush tool, hold down the ALT key before pressing the mouse button down over one path's beginning or ending anchor point, and then hold down the ALT key again before letting go of the mouse button when the cursor is over an end point of the other path. (It is not necessary to hold the ALT key down while drawing between the two points.)