JLAB_ADDPATH is in the main directory of jLab.

 JLAB_ADDPATH  Adds JLAB and JDATA subdirectories to your Matlab search path. 
 
    This script adds JLAB subdirectories to your Matlab search path, as
    well as the JDATA directory if it is found to exist. 
    __________________________________________________________________
    This is part of JLAB --- type 'help jlab' for more information
    (C) 2015--2019 J.M. Lilly --- type 'help jlab_license' for details