how to delete hidden folders from iCloud

How would it be possible for Apple devices to automatically create folders for 3rd party apps that do not even exist on your Mac. That is something I would dearly like to know.

You still have something running in the background: this is a custom folder and is not managed by Apple 🙂

If you want, you can use some filesystem watcher: macos - Is there a command like "watch" or "inotifywait" on the Mac? - Stack Overflow

Maybe someone know how to disable this synchronization from the local drive to the iCloud drive.

Turn it off in System Preferences, then you wont see the drive at all.

Doing this maybe he will also see some strange event/error in the console :-)

Anything on iCloud is on every device that you connect to iCloud. That is the point of iCloud.

Please continue to ignore the advice you are getting here, it is after all, your Mac.

The screenshots you posted say otherwise.

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No this was my last message, we gave all the suggestions we could, as you said before it's his own Mac not mine 😝

Asking for advice and then totally ignoring it is rarely seen as polite.