Where are the iCloud Files?

[MacRowland]

I found this post, it answers my suspicions.

How can I verify iCloud sync without second device?

Files won’t show up in iCloud Drive, because we sync using a hidden iCloud data store. You should see that there is data in iCloud though, if you go to the manage data area in System Preferences for iCloud. Agenda should be there, and have data. If your iCloud Drive is turned on, it should be syncing. If it is actively uploading, you will see the cloud flash top-right in the window. One way to confirm that data really is in iCloud would be to move aside your local data, and see if the data dow…

And I was able to see the data storage used.