Document: 
https://github.com/kubevirt/vm-import-operator/blob/master/docs/design.md#vmware-mappings

apiVersion: v2v.kubevirt.io/v1beta1
kind: ResourceMapping
metadata:
 name: example-vmware-resourcemappings
 namespace: example-ns
spec:
  vmware:
    networkMappings:
    - source:
        name: VM Network # map network name to network attachment definition
      target: xyz  <===== Enter here network target name doesn't work.
      type: multus
    - source:
        id: network-7 # alternatively the network can be mapped by managed object reference
      Target:
        name: pod
      type: pod
    storageMappings:
    - source:
        name: iSCSI_Datastore # maps disks in a given VMware datastore to a storage class
      target: storage_class_1

Description of problem:
In VMware mapping yaml, Network section, using "target: xyz", as mentioned in the  didn't work for me (mapping yaml creation fails). 
I had to use instead:
target: 
  name: ... 
for it to work.

Version-Release number of selected component (if applicable):
CNV-2.5

Additional info:
This might be originated from the Ovirt mapping example:
https://github.com/kubevirt/vm-import-operator/blob/master/docs/design.md#ovirt-mappings