I’m looking for a “wireless” ZWave dimmer switch that is powered only by the neutral wire - no line, no load. I would use this to control combinations of lights, each of which has its own wired ZWave switch. I’ve seen some suggestions that a wired ZWave dimmer could be used by simply not connecting a load, but I’m not sure that would work.
Any suggestions appreciated.
It can’t be done with just a single wire that I know of… Maybe one of the electricians can comment on that.
Is there a reason why you don’t want to go with a battery powered switch for this kind of set up? There are several of those that work well with smartthings and the ones from Zooz should continue to work with the new platform as they are already working on edge Drivers for them. It just seems like a simpler solution unless you really want mains power.
For example, the Zooz Zen34 is quite popular and looks exactly like a regular switch.
If you do really want Mains power, both Zooz and Inovelli have several models which can be set to “smart bulb“ mode where they don’t actually control the power on the circuit. They just send a radio message to the hub. I think those would do what you want even if not quite in the way that you imagined it. So just check their individual models for this option.
Another possibility might be the Zooz scene controller. It’s mains powered, but the small buttons work via RF, not direct current control. (You’d have to ask them if the large button can be disconnected as well)
Both Zooz and Inovelli have committed to keeping up with the architecture changes that smartthings is introducing over the next few months, which is why they would be my preferred zwave brands right now. Both have been popular in the community. 
