Thanks for the replies, John! Your explanation of how the Group Field values works was very helpful, as I could not find that information anywhere else (the update_field() page on ACF seems focused mainly on repeaters, with rows and etc..).
Unfortunately your suggestion of hardcoding default values if there is no value set would not work in my use case; I want users to be able to create blank fields if they wish, and with this suggestion, removing the field entirely would simply return the default value (not an empty space).
Do you know the simplest way to find the field keys (as opposed to field names)? It does not seem intuitive to me.
I will try to re-explore this when I get some time to work on it and keep you updated. Thank you so much for the help!
