With Madrid, assignment_group and assigned_to fields seems to be added to the Vulnerable Items table. If someone is on london and say created a custom u_assignment_group field on that table, what action are needed for this custom field.
From madrid , these fields have been added to the table and are documented here Vulnerable item fields
Assignment group : Group selected to work on this vulnerability group.
Assigned to : Individual from the selected assignment group that works on this vulnerability.
These fields were not in london - Vulnerable Item field
There is some logic written to populate a value into assignment group field by default, which depends upon the scenario
But if you still want to use your custom field on top of it with you custom implementation, you can use it . However it will be your customization and to be taken care by you.