The spec for JSON:API v1.1 mentions that "when the resource object originates at the client and represents a new resource to be created on the server", "a lid member may be included to uniquely identify the resource by type locally within the document".
However, when creating a new resource, "the request must include a single resource object".
So, it seems the only case where "lid" might be useful is to create a resource with a relationship to itself.
Is this correct? Else, what would another example be?