You can also import from Bitwarden (and kdbx) into Firefox. Then it's all nice and tidy and then pull it into a fresh kdbx. Of course, you prolly don't want to have Firefox sync on when you do this. It's getting easier to import/export data from one system to another nowadays - not just with password stores either. In the olden days, pulling data from one proprietary app and reformatting it in a form conducive to importing into the target app meant purchasing some sort of intermediary third party...
You can also import from Bitwarden (and kdbx) into Firefox. Then it's all nice and tidy and then pull it into a fresh kdbx. Of course, you prolly don't want to have Firefox sync on when you do this. It's getting easier to import/export data from one system to another nowadays - not just with password stores either. In the olden days, pulling data from one proprietary app and reformatting it in a form conducive to importing into the target app meant purchasing some sort of intermediary third party...