[label:cms_e]I cannot delete the contents in bulk, and it shows "It is under editing, so cannot be deleted."
If you display "Contents List" in "Tile" style, you may find an icon that shows "Key".
The icon means "Unlock the content from the protection for a content under editing." In case you find the icon, it means the content is under editing.
To unlock the content, please click the "Key" icon, and click "OK" for the message saying "Do you want to forcibly unlock the content?"
Then the content is unlocked and ready to be deleted.