Summary
After completing the upgrade of the Global NSX-T Manager and both my Data Center’s Local Managers and their NSX-T Components (Edge Nodes, Transport Nodes and NSX-T Manager) I went back to the Global NSX-T Manager to confirm that all the nodes are now syncronized and connected.

From this dashboard we see that we have successfully completed the upgrade to NSX-T 3.0.1 in my Federation deployment.

Note
This upgrade was carried out in my lab and you will need to understand the upgrade sequence selection for your environment.
I hope you found this useful, for full details you can refer to the VMware Documentation.