If you buy or make menthol flavoring, just a tiny drop flavors 5 ml. I bought this
Perfumers Apprentice - Menthol Liquid (PG) and just add a drop to juice without worrying about nic levels when I want to vape menthol. Very useful stuff. That $1.40 worth of flavoring will last me years since I only occasionally vape menthol.
If you visit the DIY forum you can learn more, but from what I understand you can get menthol crystals from your pharmacy and some PG and make your own for almost nothing.
If you mix regular already mixed menthol juice, you'll have twice as much of the loser juice. Flavoring won't increase the volume and cheaper.
Menthol can mask bad flavors most of the time and good when you lose your tastebuds.
Try it, you'll like it.