there is a backup / restore approach for openHAB
this one should copy the homekit configuration.
if you only want to copy homekit configuration and pairing then
- copy homekit.json for pairing information. in my case it is /var/lib/openhab/jsondb/homekit.json
- copy homekit.config for configuration. in my case it is /var/lib/openhab/config/org/openhab/homekit.config