Ah, I get it now, this video (14:10) shows how you can use a standard toggle switch as a dimmer in momentary mode. At 36:55 it also shows a 3 position momentary switch setup.
Yup, and it doesn’t even need to be configured as a momentary switch if you use the night mode feature.
The following is a suggested wiring diagram for the Fibaro Dimmer2 (current) model when used in a staircase implementation. It is from a UK reseller so I cannot comment as to whether this approach is appropriate for US houses.
As you can see only one Fibaro module is required and both switches would be 3-way momentary aka retractive switches. The same article also shows using 3 (or more) switches on the same staircase circuit.
Typically the micro modules are fitted in the ceiling here in the UK because fitting even one behind a wall plate is a tight fit and multiple ones (for multiple light circuits) pretty much impossible.
With all US manufacturers having utterly failed to produce wired smart switches for the rest of the world, using a micro module like Fibaro with momentary/retractive switches is pretty much the only effective option here in Europe.
I’m in the UK. My existing back boxes are 25mm, no neutral, I’m happy to do the single switches myself using deeper back boxes.
Does anyone know if the new Shelly Dimmer will work in the same way, at £20 compared to £45!
Shelley looks to be Wi-Fi only. I am sure you could get it to work, but it would need some programming. If you need a few and are prepared to do the coding then why not. IMO its better to stick with the Fibaro Dimmer 2. They are rock solid and have local execution on SmartThings.
Shelly have confirmed that the Dimmer can work in the same way as the Fibaro Dimmer so will work with a 3 pos switch. They can be added to ST or HE with a little work too. I’ll try one out first and report back
If you are in communication with Shelly could you ask them about adding HomeKit support. The devices are as mentioned WiFi and HomeKit supports WiFi or Bluetooth devices.
In fact there is unofficial firmware to add HomeKit support but official support would be preferable.