To manipulate outline information on the currently highlighted node, use "Outline Edit" mode (click on the icon in the tool bar or use the Toggle Outline Edit command, in menu Edit / Modes / Edit).
Figure 6.5
In this mode, the left button is used to select and move a point on the outline, and the right button adds a new point after the selected one. You can also use the left and right arrow keys to move around the outline. The Erase command (in menu Edit) deletes the current outline point. (so does the Delete key).

When done editing the outline, switch to standard selection mode (the Click/Zoom/Wire command, in menu Edit / Modes / Edit).