I’m trying to control a fibaro radiator thermostat. From the manual, under “2. Additional functions” it says I can give it a 4byte value to control specific parameters. The problem is that the z-wave integration only allows a value 0-31. Am I missing something, or is this a bug?
The HA zwave-js integration does not control the definition of the device configuration parameters, that is provided by the zwave-js driver. You would need to submit an issue or correction to that project.
Done.
In the meantime, is there an easy way to work around this problem? Either use my own fork as a driver for this specific device, or is there a way to intercept/override the configurations?
I’m fairly new to HA, so handholding is appreciated 
Instructions are here: https://zwave-js.github.io/node-zwave-js/#/config-files/overview
It’s difficult to do if you’re using an addon, hard to get to the container files. If you are using docker standalone, you can add the file to an external directory. https://zwave-js.github.io/node-zwave-js/#/usage/external-config.