Extenders were useful in the older versions of the wave, but in the last two versions pretty much every device is already transmitting at maximum power so just about any any mains powered device will act as a repeater, which is all the single purpose extenders do. And you’ll get more value out of a dual purpose device like a light switch, pocket socket, in Wall relay, or plug in sensor.
If you do buy the single purpose extender, it should pair as a switch and after that it will just repeat messages. You won’t be able to do anything with it from the network. You won’t get any data from it. It’s just a repeater. And if it’s one of the older Z wave classic models, it will extend your mesh less than any mainspowered Z wave plus Device.
I’m just saying these days most people would just get a pocket socket instead of the single purpose repeater. It won’t cost you much more and you’ll get a lot more use out of it.
But if you happen to have the repeater and want to use it, you can just use a generic zwave switch device type with it. It doesn’t do anything anyway.
If you want a fancier DTH that won’t look like a switch, @jhamstead has a good one that clears out a lot of the clutter and alerts you if it stops working. It should work fine with any single purpose extender.
I have a couple of them and use them to reach my shed at the bottom of my garden.
They certainly do work for my Foxx door sensor on the shed door.
However, I bought them because they were cheap and would probably buy the foxx project plugin sockets if I were doing it again.
At Maplins they are only £5 more but you have the socket as well as a repeater