If you have the 'Good Lock' app that Samsung released for customisation (or are able to download it) there was a Bixby Routines + released just the other day on my phone. Once downloaded it just adds a few extras advanced options onto Bixby Routines.
I recon this could be done by going to 'Plug-In' and attempting it via a 'Touch Macro'.
It essentially records the process of going from point A to B whatever that may be. In your case it would be the start to finish process of switching the WiFi calling from the start of the settings page via what looks like a screen recording process but it is just every touch on the screen you make & the exact location and once saved carries out your process super fast. I'm guessing it is accessable via settings as you need to choose an app and settings is in there I checked. As long as the pages always have the same layout from start to the finish of the process this should work. I failed to get one working because what I was selecting was a specific playlist on amazon music but it moves around based on when it was last played so because it records where I touched on the screen, rather than what I touched, it selected different ones but I've realised an easier way to do this now thankfully.
If you have access to it I'm sure you'll see what I mean. I would attempt to replicate this right now but I'm awake in 4 hours 😴 Hense why I'm here typing this long post to sabotage myself.
Hope this helps. Good luck.
