As for the en-dash I use the option for additional substitution:
- within substitution at the “auto-correction” options
- un-check the “replace double hyphens with em-dashes” option
- check “enable additional substitutions”
- chose “edit substitution”
- klick on the plus-bottom
- fill in the replacement - I use now double hyphens and replace it with an en-dash
I am pretty sure you find a similar way to replace any unused sign with german quotes as well. As I use “<<” to replace it with “«”.
Cheers Simo.