Migrate Citavi 2 JabRef
This could be a simple (python or anything else) script helps you migrating your bibliographic data (including attachments and groups/categories) from Citavi to JabRef.
There is no code actually. But if you really need to migrate a Citavi project to JabRef I can help you with this. There is a code base in the sibling project Migrate JabRef 2 Citavi where you can see how the Citavi data structure works.