question

Some trig will be involved for this and the commands you will need are drawtomodelscale() and either drawrect, drawrectangle or drawquad(). (fglRotate() might also help)

You'll also want the other node coordinates relative to the current node for a given port :

Vec3 otherloc = current.outObjects[port].location.project(current.outObjects[port].up,current);

and then the angle from one node to another will be

Math.degrees(Math.atan2(otherloc.y,otherloc.x))

If you were using an up to date version the vector logic is much simpler:

double pathwidth=2;
drawtomodelscale(current);
for (int n=current.outObjects.length;n>0;n--) {
Vec3 otherloc = current.outObjects[n].location.project(current.outObjects[n].up,current);
Vec2 other2=Vec2(otherloc.x,otherloc.y);
Vec2 unit=other2/other2.magnitude*pathwidth/2;
Vec2 leftoff=unit.rotate(90);
Vec2 p1=leftoff;
Vec2 p2=-leftoff;
Vec2 p3=p2+other2;
Vec2 p4=p3+leftoff*2;
drawquad(view,p1.x,p1.y,0,p2.x,p2.y,0,p3.x,p3.y,0,p4.x,p4.y,0,0,1,0);
}