As far as I know, parameters must be configured using the z-wave control panel or service. I suggest to allow configuring parameters in the configuration files, so that it is possible to store this configuration (with comments). This would make it much easier to restore a complete system to a previous state.
No idea if this is technically feasible but it would be super convenient.
I am not sure if and when the controller checks the parameters of all devices, but maybe transferring to a single device/all devices should be a manual command triggered in the control panel - that would be no problem. In addition, it would be ideal if changes in configuration files are detected and transferred automatically. This would require some sort of cache (as far as I could see, parameter changes are not stored in zwcfg*.xml).
Depending on the device, the parameter should be stored on the Z Wave device. Example: GE Z Wave switches and outlets store the parameters locally on the switch. It’s a “set it and forget it” configuration.
Agreed though that parameters not stored on the device should be allowed to be set from a configuration file. You can create automations that call the Z Wave service and pass JSON format commands.
I know that they are stored in the devices. But what about when a device is reset, or changed? Or you want to review the parameters? I would prefer the way of setting those parameters to be through configuration files.
An alternative would, of course, be to keep them as automations and trigger when necessary. However, using node_id instead of entity_id makes it harder when restoring parameters.