Move the subelement to the point at a given distance along the connection path but do not auto-orient it according to the path's gradient. Use a positive number to define the distance from the source of the link and a negative number from the target of the link. It is valid only within the LinkView context.

link.attr('rectSelector', { atConnectionLengthIgnoreGradient: 30, width: 10, height: 10, fill: 'red' });