Hi there,
We're sorry to hear about your difficulties. Would you mind telling us if it is a shared library?
The latest Libraries update allows you to create subfolders by entering slashes ("/") in a group's name. Libraries with existing groups containing slashes must either be migrated to use "-" as a separator instead or upgraded to apply the new meaning of a slash in the name, which will create the groups and subgroups however, the library is locked until you decide which change you want to do. There is no way to revert that at this moment.
Let us know if that helps.
Regards,
Tarun