So for confidence in a theory to grow we don’t require that all of its features be verifiable; a robust and varied assortment of confirmed predictions is enough. Scientific work going back well over a century has accepted that a theory may invoke hidden, inaccessible elements—provided it also makes interesting, novel, and testable predictions about an abundance of observable phenomena.
It may give one confidence about the theory's claims regarding unobservables, but it can't declare that those unobservables are any more real than anything imaginable that doesn't contradict observed reality.
