One idea to build on extra field is for the fields to have a type. Lets say NFC data.

A user is using the app on their phone and they want to load in their info using a nfc smart card into a field named user.
They can use nfc on their phone to get this data into the field.
There is a API for this https://developer.mozilla.org/en-US/docs/Web/API/Web_NFC_API

Same thing for maybe location.
https://developer.mozilla.org/en-US/docs/Web/API/Geolocation_API

So when we are creating extra fields we need to be able to select a field type.
Type could be Date, Time, Location, NFC and so on.

Cool thing is that this works on Android, iOS and PC.

Maybe we could start with date, time and location.

Hope you understand what I'm saying.