You can move or copy a folder (or subfolder) using the Move/Copy option under Folder Options.
Move will re-file that folder in a different location. It will no longer be "filed" in the previous location.
Copy will copy the folder and its contents to a new location, creating a separate copy in a new location.
To move a folder to be a top-level folder, simply select the cabinet name at the top of the folder tree.
NOTE: Even if you have Folder Access Inheritance enabled in the cabinet, when you move a folder into another, that folder and its tree will NOT inherit the access of the new parent folder. Because of the potential to make a mistake, folders do not inherit access from other folders. If you do this, you will need to manually adjust the folder's access after moving it.
When copying a folder, you will have an option to rename the folder as it is copied.
There will also be an option to copy just the folder and subfolders (if any) and not the contents of the folders. By default, the checkbox for "copy all the documents in these folders too" will be checked: