I am now converting my devices from Security S0 to None. I find it odd that I can't just use my secondary controller to set already paired devices to S0... I tried, but no luck.
In case anyone is interested, here is how I proceed:
- Using the "Z-Wave PC Controller" software on my PC with a UZB dongle, select "Remove" to exclude the device
- Using the software, select "Add" and then put the device into inclusion mode to include it again. This sometimes takes a couple of tries depending on the device...
- Once the device is included, select it from the list on the software, click on the "Security Scheme" button and select "None".
- Convert the device number into hexadecimal
- Go to the device in Hubitat and Edit the "Device Network ID"
- Enter the hexadecimal value under the "Device Network ID" (Not doing this will create a new device in Hubitat using the "Type"/Driver name once Hubitat finds it...
- Repeat for all devices
- Power off the hub, unplug it for 1 minute, plug it in again
- Go to "Z-Wave Details" and see that the device(s) are now in the list of devices at the end of the list. (Rebooting seems to be the only way to get the new device(s) to appear... Unfortunately, as far as I can tell, there isn't some sort of refresh button for this...)
- If the device shows "NOT_RESPONDING" or "FAILED" at that point, press "Refresh" or "Repair" while also pressing the button that makes it join the network over and over and over and over again until it is finally "OK" again... (Maybe there's a better way to do this... If so, I don't know it yet...)
- In Hubitat, do a "Repair Z-Wave". Not sure if this is required or not, but I suppose it can't hurt...
It is very difficult to accept this non-sequenionalism... very difficult... 
