Huh. Protonmail doesn't have "contacts". So you can't export or save them. Nice trick for customer retention.
EDIT: my bad, Contacts exists; I'd turned off the right sidebar (tiny arrow 80% bottom right edge) but there is no export except individual vcf files. 450 of them. These can be file attached to email l but only 100 at a time. Contacts doesn't appear in settings etc.
Most annoying.