Changing the name of app containers in the iCloud Drive on OS X?
After doing some searches in the Library folder, the plists and the app icons of the app containers are located in:

~/Library/Application Support/CloudDocs/session/containers/


Change the BRContainerName property in the plist of an app container, and restart the Mac. The iCloud Drive in the Finder will then display the changed name. As shown in the following screenshot, the app folder "Documents" was supposed to have a longer name "Documents by Readdle".



Without locking the plist, the name still hasn't been reverted after a restart. So it is still unknown in what circumstance the plist will be reverted back to the original version by the bird daemon. But given the fact that the plist specifies the corresponding app version, it will probably be reverted on an version update to the container-owner app.

P.S. Document Picker on iOS and the iCloud Drive web app are not affected by this.