Please note the list of VDTs available when adding a VDT node are those that are not already linked to another VDT, this was implemented to prevent the system from getting into a loop when evaluating the VDTs.
A VDT that is already linked will have a link to the VDT that it is linked to, as displayed below:
![](https://s3.amazonaws.com/cdn.freshdesk.com/data/helpdesk/attachments/production/5118522112/original/QsRt9Mp2APKt0uIVrYi64RHZPj0cH2yymA.png?1579167275)