This is a mod that doesn't alter any of the in-game horse harnesses. It must be added using an editor like Edit Lord or Saddled Edge because it is a special ID.

It is intended for people who wish to have a different-looking horse, but not in a way that looks like a medieval jousting knight with a skirt-barding.

In order to do this, you need to download this mod, and then drop the Enbarr Horse Harness folder inside your common \Mount & Blade II Bannerlord\Modules folder.

After that, you need to make sure that it's checked as active in the launcher.