There is a profile import/export. Nothing cryptic about it that imports that information along with all of your settings for new installations. What is missing is a sync process. I have no idea if that is included in Thunderbird sync. I have not heard a release date for sync. But I would assume this would be included in that.
This is about treating Remote Content Exceptions as a separate entity, so they can be easily moved into a NEW/different installation. The Address Book for example, has that flexibility. You can search it, and you can export/import it. Alone.
Copying the entire profile along with all the other settings is different, and not really relevant.
Carefully building this list over time is no simple task. If you have many entries, rebuilding it from scratch is a nightmare. That's why a separate backup would be most helpful.