Anything with a GUI seems really daunting to specify. And then later you need to update specs to match GUI if you make any changes and you need to decide which is wrong: the implementation of the specification.
I’m not even sure what would be gained by formal verification of a GUI
There are approaches to GUI which are closer to formal specification than what is currently in use. Look at HotDrink for instance: https://tt.utu.fi/soft/hotdrink-gui-programming-with-dataflo...