After the excruciating installation process of the tModloader dedicated server, you may notice that you will not be able to change mods that have server-side configs, as it will reject the change and say that only the host can change it. You may think of giving yourself admin but there is in fact no way to allocate yourself that permission as of the post date (apart from using a mod, of which I don't know one that does the job).

Instead, you will need to change it in the ModConfigs folder. It however doesn't provide all the config files, so this guide shows you how to get them.

Steps

1. Figure out the mod you want to modify settings for.
2. Go into workshop from the menu, find the mod you want and change the server side settings that you want.
3. You can now find the generated config in Documents/My Games/Terraria/tModLoader/ModConfigs. It should be the same name as the mod you were changing.
4. Copy that file into your dedicated server's ModConfigs.