Menthol is difficult to reproduce in an ecig. Menthol crystals are mixed into tobacco during the making of cigarettes. I know this because a friend of mine used to work at the local B&W plant that made Kools. She talked about going home after a shift with a menthol glow from head to toe just from being around it. The menthol crystal hopper had to kept full by dumping in bag after bag of crystals.
Every menthol juice I've ever tasted was more like a mint Lifesaver than a menthol cigarette. Maybe someone else here has the key. I don't know of anything that captures the true menthol in tobacco. Maybe there's a temperature associated with burning that releases a different sort of flavor than in
vaping (boiling).