On the A320 neo there’s an overhead switch in the lower-right labeled “wiper” with options “off, slow, fast”. It has an “inop” tooltip and can’t be moved. Is this it?
[Update] There’s an identical control in the lower-left which does operate. The wipers do move. No idea if they function for getting rain off the surface yet.
[Update 2] Can confirm they do nothing to get rain off the windshield:
