I was able to delete a folder that had a list underneath. But I DID NOT see this because it was not approved for me. In other words, I not only deleted the folder (I thought there wasn't a list below because I hadn't released it), but also this list. There MUST then be a notification that the folder cannot be deleted!

Means:

Delete folder > Check whether list below yes or no > if no > Delete folder

Delete folder > Check whether list below yes or no > if yes AND lists released for me > Ask if really delete > then delete folder

Delete folder > Check whether list below yes or no > if yes AND lists NOT approved for me > message “Folder cannot be deleted”

This is really important because it means that tasks have disappeared that should NOT have disappeared. Simply because I couldn't see them.