vm_vdr_contact table is not installed when an instance only has 'Vendor Manager Workspace' plugin (com.snc.vlm.vmw).
The table is only installed once 'Vendor Core' is installed, but Vendor Manager Workspace does not include this as a dependency.
vm_vdr_contact is not used by ITSM Vendor Manager workspace. The application uses sys_user table directly for maintaining contacts.
As a solution for now the development team has suggested adding the users as contacts of their respective core_company records, like the screenshots I've attached. This is understandably not an ideal solution, but better external user concept will be delivered in a later release.
The Vendor Manager Workspace (com.snc.vlm.vmw) plugin is also under deprecation from San Diego release onwards.
It will be replaced by a new Vendor Management product from Rome release and in coming future releases we have plans to add external users concept.