I cannot create a Mail subfolder on iCloud. When I create one it shows up momentarily and disappears. It is not hidden as it will let me try to create it again, appear, then disappear. I have restarted Mail and rebooted the computer. Cannot find anything on this anywhere online.
iMac 27″, macOS 10.15
Make sure you are not using only a web icloud account Web-only access to iCloud - Apple Support
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The mail account should be configured with apple mail application Add email accounts in Mail on Mac - Apple Support
Then create folders and subfolders from www.icloud.com see the article Organise email with folders in Mail on iCloud.com - Apple Support
Cannot create Mail subfolder
