also if you want you can just put interface mods into the folder that is already being used for the map updater. that folder (default of eq2map) is your custom ui directory and is already all set up in the eq2.ini file.
OR since you use the updater you dont have to make eq2.ini. if you make a new custom folder you can go into the options for the updater and there is a dropdown for what custom folder to use, choose whatever one you want and it will set up your eq2.ini file to use that folder
hope that makes sense, if not let me know.