int addpoint(int geohandle, int point_number)
Creates a new point with all the attributes and group memberships of the point with the given point number.
int addpoint(int geohandle, vector pos)
Creates a new point with the given position.
A point number for the created point, or
-1 if the point could not be created.
You can use the return value with setpointattrib to set attributes on the new point, however it may not be the final number of the point.