Creating zero length CBUSH elements (for RBE3 support)

In my model, I am attempting to use RBE3 elements as supports to avoid artificial rigidity imposed by RBE2s. Because a support cannot be attached directly to an RBE3 element, I am trying to create a zero length CBUSH element with high stiffness, as suggested in this help document.

However, since the CBUSH element is a spring that requires two nodes to be specified, I don't understand how to achieve zero length without selecting the same node for the ends (which gives the error 'The independent and the dependent nodes are the same'). This post indicates that it is possible to create coincident nodes, but when I attempted to create a temp node at the same location as the center of my RBE3 (Geometry -> nodes -> x,y,z), it fails to create a distinct node that I can select in the spring creation panel.

My questions are:

1. Is it possible to create coincident nodes?
2. If so, how is this done?
3. If not, how do I create a zero length CBUSH element?