End user is unable to add new Network Card from Aria vRA 8.x portal for existing VMs after VM is migrated to Aria from vRA7.x.
In vRA 7.x there was an option to reconfigure VM where user could add new Network Card as per requirement.
VMware Aria Automation 8.18.1
We cannot add Network Card in 8.18.1 and there is a way to add a NIC to a VM, but it is a custom solution. The solution was created for earlier version of Aria Automation.
But in the new version of Aria Automation, NIC will not appear in the deployment canvas, i.e. It will not be visible from Aria Automation 8.18.1. add NIC was a standard thing in vRA 7.x, not in vRA 8.x
Recommendation: customer can contact with their TAM/SAM and they can raise feature request to have it in 8.x ( or 9.X classical/VM apps )