No result configuration to include chat feature

Hi Liz,
Sorry to ask but a quick question about this reply you shared.
For the Universal search default no result text, when you say we need to update the config.json file, I am not sure to know which one it is. You mean index.json or any other file? Because I can find this “noResult” part for [vertical].json files but not in the index.json. I tried to add it to test but either it is not supposed to work this way or I was not able to find the correct syntax.
Could you please confirm which file needs this update?
Thanks a lot!!!