The lister displays all available filetypes. Worker supports hierarchical filetypes, so every filetype can have any number of subtypes. This can be used to group several similar filetypes. For example, there can be an image type, which does not contains any filetype description but only a default action for showing images. Each real image type can be a child filetype so it can be used to describe the actual filetype but does not need to add a action to show this image type if the default program can be used for this type.
Subtypes will be checked if the filetype tests of parent type matches the current file or the parent type does not use any tests. The action of the parent type is used if the action list of the type is empty or the "parent action" command is used. The "no operation" command can be used to not execute the commands of the parent type.
There are 4 special filetypes, which cannot be removed and do not have parent types. It is possible to configure these types but the pattern/filecontent will not be used for filetype recognition.