There’s a line in the config.json that looks like this
Under it you can over-write any of the settings that are available to you in your singleplayer advanced tab where the settings you need are located.
If you want an example, this is what i did for one of my maps. The thing before the dot is the category in which the setting is in (in the singleplayer advanced tab). The bit after the dot is the name of the setting (replace any spaces with underscores). Put a comma after every line except the last one