Henning Hraban Ramm wrote:
> I'd like to typeset a text in both German and Swiss German orthography,
> i.e. I'd like to expand "s (or the like) to ß in German and ss in
> Swiss German mode,

If everything is set OK in the regime you're using, this should work:

\startmode[swiss]
\definecharacter ssharp {ss}
\stopmode

Mojca