ah ok, no worries - I think it's similar to Redux largely, which unfortunately includes being severely incompatible with nested state values.

In redux I use functional lenses to create composoable getter/setter functions to handle deeply nested data safely. I do that even without redux, but it is very useful there. Take a look at the lens functions in Ramda, or safety-lens

I'd never thought to use lenses for this. Thanks for the advice, that actually really helps!