Community:World constraint
From VRChat Wiki
World constraints allow for constraints to follow a specific point in world space. Mainly used on Avatars to lock a object to the world and not follow the avatar. This works by referencing a prefab in your assets instead of a Gameobject in the hierarchy.
Before VRC Constrains were added with the "Freeze To World" option this was the method used to freeze things to the world.
Setup
To setup you need a prefab in your assets you can reference. Its suggested the prefab to be a empty Gameobject, don't need anything else on it. Then drag and drop the prefab from your assets to one of your constraints sources.
The prefabs transform can be changed and the constraint will follow what ever its set too.