Eurotronic Spirit Z-Wave - external temperature sensor

There are no Spirit installations with HA/ZJS, i cannot write or test anything.
Only installations with Vera are exists.

But you can oversee ZJS documentation here:
https://zwave-js.github.io/node-zwave-js/#/usage/custom
Actually Spirit waiting for incoming SENSOR_MULTILEVEL_REPORT, with precession 2.
If you t. sensor can send report to associated devices, you can link it at Z-Wave layer and do nothing in high-level logic.