Access App State variables dynamically in Custom Widget

Hi,
i created a custom Text Form Field Widget, where i am setting the value of an App State Variable like this:

FFAppState().valueAmount = text;

To make this widget reusable, i want to use a parameter, lets say "appStateIdentifier", and use that to dynamically access the correct property of FFAppState() (which in this case is the App State Variable). Usually i would just use a Map to achieve this, so i could use something like

FFAppState().setValue(appStateIdentifier, text);

But i don't think there is access to the FFAppState class?

Am i missing the obvious here?

P.S. Screenshot is required, so here you go lol