substituteFrom possible only from same namespace where Kustomization stored

[everythings-gonna-be-alright]

https://github.com/fluxcd/kustomize-controller/blob/a1a33f2adda783dd2a17234f5d8e84caca4e24e2/api/v1/kustomization_types.go#L223

In my case, the command created Kustomizations in different namespaces. Such as monitoring Kustomization -> namespace monitoring logging Kustomization -> namespace logging and so on.

How can I share basic variables between all clusters in this case? Why is it restricted?

.spec.postBuild.substituteFrom[0].namespace: field not declared in schema