AFAIK there is no node like “GetRandomPointOfCone”, you need to do it manually yourself. You could choose a point of origin, an angle and a radius. Then a random point inside the cone would be
x = origin_x + cos(random_angle)*random_radius
y = origin_y + sin(random_angle)*random_radius
z = z
Then you take that point, and use “ProjectPointToNavigation” (and I would not set the query extend there to all 0, since AFAIK that is how far it looks to get that point onto navigation, so z should not be 0).