To use Desktop and Document in iCloud must both Macs be same OS?

As per the article https://support.apple.com/en-us/HT206985

Access your Desktop and Documents files on another device

When you add your Desktop and Documents to iCloud Drive, all of your files move to iCloud and any new files you create are automatically stored in iCloud too. Then you can find your files on all of your devices.

If you want to store your files in iCloud Drive and another cloud storage service, you can keep copies of your files in both, but you can't keep folders from a third-party cloud service in iCloud Drive. You can keep your other cloud service folders in a different place on your Mac, like the home folder.

Your files upload to iCloud each time your device connects to the Internet. Depending on your Internet speed, the time it takes for you to see your files on your other devices might vary.

Right click in the column ( below document ) and create a new folder drag and drop the document into the folder ( make sure read and write permissions are correct https://support.apple.com/en-in/guide/mac-help/mchlp1203/10.15/mac/10.15 see the article https://support.apple.com/en-gb/guide/mac-help/mchlp1774/10.14/mac/10.14

See the article https://support.apple.com/en-gb/guide/system-information/syspf9b375b9/10.14/mac/10.15

Choose Apple menu  > About This Mac, then click Storage. 

The categories shown contain the various files on your Mac. (If your Mac has more than one user account, the categories shown are for the user who’s logged in.)

Note: The categories do not correspond to specific folders on your Mac.



Have you made all items of the Finder Sidebar visible in the Finder > Preferences, Michael?

You may want to check the Finder > Preferences > Sidebar. Make sure, the iCloud Section of the sidebar is enabled. The main Documents folder for each Mac should appear in the iClouds section of the sidebar; the Favorites may be showing you local folders in your home folder. Are you seeing one or more Documents folders on iCloud Drive?

The Documents folder each mac is syncing with is the one you are seeing in the iCloud section of the sidebar. Put a file with the name of your mac there, so you can see, where it will appear on the other mac.

iCloud is teaching us to be patient 😀

I am only keeping a small selection of my documents on iCloud drive. Most documents and data, that I do not need on all my devices, are stored in local folders on each device.