Conan Exiles offers a Dreamworld DevKit, that can be used to create a mod. Remember these mods work to sell on single player, there is no surety whether it will work well on multiplayer, but there is a different way of doing the same.
Below are two different methods, first is for using the mods on single player that works well without issue. But there can be a problem with game load time. Second using them in the multiplayer.
Method 1 – Using Mods in Single Player
You just need the mod file. Just move the same to Conan Exiles\ConanSandbox\Mods. The game will load the same. If you are not interested in creating the same you can go ahead with a subscription of Steam Workshop. The mod files are a single archive file with .pak extension.
Method 2 – Using Mods in Multiplayer
There are two ways, first running on Client Side and second on the Server side. If you want to use your client side mods on another server it is important that the server must have them running. Or else you won’t be able to connect. The server will notify you the list of mods your game is missing. Second is building a server with different mods and allowing other players to use them. For that follow the below method.
Collect all the mods with extension .pak and move them to a dedicated server folder. For example ServerModFolder/ConanSandbox/Mods/.
Next, you will need to create a text file in the same place which has a list of all mods with its full paths. For example modlist.txt. Below should be the format. Mod name with its extension and an asterisk before the path.
Next, when clients try to connect to your server, they will get a message box with a list of mods required. Without the mods, clients won’t be able to connect. You can also do this by using the PingPerfect server as mentioned in the game manual. You can use this tool to create a dedicated Mod folder that can be used on the server. The process is pretty simple. Just install the client, create the server and then access ConanSandbox folder via file manager. Create a folder Mods in it and upload all your .pak files with modlist.txt in it. Reboot the server once before using.