Aside from the normal controls, there are some others:

E - enter editor
Q - exit editor / start game
Up/Down/Left/Right Arrows - move camera
F - zoom in
R - zoom out
Z - remove last polygon point in current polygon
Backspace - remove selected polygon
Mouse left - add a point to the current polygon
Mouse right - close/deselect the current polygon
S - save the map
[ and ] - cycle through polygons
X - remove the selected course point
C - place a course point
; - previous course point
' - next course point

All polygons must be counterclockwise.  If you have any more questions, email me - dcower@gmail.com