Thanks for your support of Codebook and posting the discussion forum, although I’m sorry to hear about the issue you’re experiencing when attempting access Codebook preferences.
Delete and re-install
I think this is a good first step to troubleshooting.
then restore? Or is there something less drastic to try?
Your Codebook data is stored separately from the application installation, so deleting Codebook and re-installing should leave your data in place and you shouldn’t have to perform a restore operation.
If you’re still experiencing the issue after re-installation could you open the Console app via Applications > Utilities > Console and search for “Codebook” to see if there are any messages/errors related to Codebook in there after attempting to access preferences?