After our discussion is in the other thread, I know that you’re just trying to figure out what automations to set up using the official SmartThings features so that you have three switches controlling the same fixture.
I’m not sure exactly which model Nutone switches you have, though, but they are all three showing up as devices in your SmartThings mobile app, right?
If so, you should be able to use the official “mirror” feature so The master switch will follow the auxiliary switches, turning on when they turn on and turning off when they turn off. You would need one rule for each of the two auxiliaries. That creates your virtual 4 way.
After that, it depends in part on your wiring. Normally with smart switches the auxiliaries do not control the load. Instead, they just essentially act as remotes for the master, telling the master to turn on or off.
But if they are wired more like a dumb switch so that you are closing different circuit branches as you change different switches it’s going to be a lot more complicated. ( you can tell that if the auxiliaries work to turn the lights on and off even when you haven’t set up any rules at all. If so, the wiring may not be correct for smart switches.)
That’s one reason the model number matters. There are some auxiliary models in that line which don’t have the wiring to control the load, so that just simplifies everything.
Tagging @prjct92eh2 @jkp