Driver recertification is required any time a certified driver is modified, which includes the modified VCP or USBXpress driver output from AN220. The driver recertification process is always changing and Microsoft is currently migrating to a new "Hardware dashboard" system. The current version of the application note AN807: Recertifying a Customized Windows Driver Package explains the resell process in the new system.
So far, all the VCP drivers have been moved to the new dashboard, however, the USBXpress drivers are still present in the old system. The timeline for the completion of the migration is decided by Microsoft.
Hence, if you are looking for instructions on reselling the USBXpress driver, please read through the older version of AN807 (attached to this article).
For VCPXpress drivers, you can always obtain the instructions from AN807 here - https://www.silabs.com/documents/public/application-notes/an807-recertifying-a-customized-windows-driver-package.pdf
As of this update, USBXpress (Direct Access) drivers are now migrated to the new Microsoft Hardware dashboard system. Thus, customized USBXpress drivers can certified according to the same method as customized VCP drivers, as given in the link to AN807 above.