Help add buff duration variable in config files

hey folks, have l2 acis project, and my DataPack did not includes buff duration variable in property files, but i need to add one.
so I'm searching for some advices or guides how to do that, where to pass parameter or may be some one has already written java file with can put in server java files and just set variable in configs.
ofc i know they way how to change it manually one by one(in xml files)  but it takes tooo long to do that, and as you know "time = money"  😄