Graf Zeppelin as a carrier fleet in being

Could a completed Graf Zeppelin have made a meaningful difference in the war?

Yes as a fleet-in-being threat, forcing British carrier deployments and construction even if it rarely sailed.

Graf Zeppelin did not need to be an excellent carrier to alter Allied force allocation. Its existence as an operational fleet unit would require Britain to keep counter-carriers ready in the North Atlantic and could accelerate Audacious-class completion even if the German ship spent long periods in harbor. British planners could not safely assume that the carrier's serious design faults would prevent a sortie. Like Tirpitz, the ship could impose costs as a fleet in being, tying down ships and aircraft until she was destroyed.