To give structure to the navigation of your website .wfc files can be organised into subfolders within the "content/pages" folder. There is no restrictions as to how many files or subfolders you can have (although your site designer may have somthing to say about that).
Each folder and sub-folder created in the contents folder creates a navigation link in a similar way to .wfc filenames.
Each folder in the "contents/pages" folder (including the "contents/pages" folder itself) should have a file called default.wfc - it is the contents of this file that the built web site uses for the navigation link generated by the existance of the folder.
Navigation links derived from folder names are blended with navigation links derived from .wfc files. Like filenames folder names may contain a prefix to force a particular order to the navigaion links within the same parent link.
Logically there is no difference between a file called, for example, "The Flintstones.wfc" and a folder called "The Flintstones" with a file called "default.wfc" within the folder (provided the two files have the same contents). However to add Navigation links 'Under' "The Flintstones" such as "Barney" and "Fred" requires the "The FlintStones" folder to be created to house "Barney.wfc" and "Fred.wfc"
Restrictions
foldernames must be of the form linkname or priorty.linkname
linknames must be unique within a folder i.e. the file "a.Help.wfc" and the folder "Help" can not be in the same folder. Additionally the linknames must be unique within a folder after non-alphanumeric characters are removed i.e. the sub-folder "Six+Two" can not be in the same folder as the file "Six-Two.wfc"

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