NSX 6.4 introduces a new feature called the NSX Upgrade Coordinator that helps in planning and performing an end-to-end NSX upgrade. The NSX Upgrade Coordinator provides an option to perform a one-click upgrade, where it will upgrade the entire components in one session, or a planned upgrade, where you can custom the upgrade plans and organize components into multiple upgrade groups. It also provides the upgrade progress status, and pre and postupgrade checks, which improves the overall upgrade operations.

The NSX Upgrade Coordinator is available as a new Upgrade Coordinator tab in the Networking & Security | Installation and Upgrade menu, both from the vSphere Web Client and HTML5-based vSphere Client UI, as shown in the following screenshot:

Anthony Spiteri has a blog post that covers in detail how this NSX Upgrade Coordinator works: https://anthonyspiteri.net/nsx-bytes-nsx-6-4-ui-enhancements-and-upgrade-coordinator/