Although LOCAL_CONFIG_DIR is talked about in Chapter 2, and is present in the example global configuration file in section A.12, it appears to be missing from the list of system wide configuration parameters in section A.3.
Moving to 1.3.2. LKB
LOCAL_CONFIG_DIR was added to System Wide Configuration File Variables: LOCAL_CONFIG_DIR Directory that provides an easy way to extend the configuration of MRG Grid by placing files that contain configuration parameters inside the directory. Files within this directory will override settings from the global file for that machine. >>> VERIFIED