vkdt ships with a couple of default processing graphs. these are defined in the
installation directory as default.i-* and default-darkroom.i-*. you can
override these by placing a (modified) copy in your ~/.config/vkdt directory.
the suffix is the name of the input module used for certain file types, for
instance i-jpg for jpeg image files. the file itself contains a human
readable .cfg file, so you can edit an image to taste and just place the
resulting .cfg file there as default.
the filename of the individual input files will be appended to the config.
the -darkroom infix means that it is used when entering darkroom mode. this enables
you to use faster processing/take shortcuts when rendering thumbnails.