O original Acordo de Schengen menções
a transit visa authorising its holder to pass through the territories of the Contracting Parties once, twice or exceptionally several times en route to the territory of a third State, provided that no transit shall exceed five days.
Parece que isso não existe mais (veja, por exemplo, https://ec.europa.eu/home-affairs/what-we-do/policies/borders-and-visas/visa-policy/apply_for_a_visa_en) Quando foi abolido?