How Can I Pass an Array to a Server Action to Write to the Database?

@Antony - I'm working on a complex query at the moment to pass data (29 + filters, each can have multiple data points) via a SC form to an API. So, while not exactly the same - the intent of passing data from a form to SC so you can then action has similarities and you might find the following useful, and a way to avoid using side data store.

SC forms can output as nested JSON depending on how you name the input.

Take a look at:

and
https://www.w3.org/TR/html-json-forms/

I'd say you could nest the questions and answers using the implementation options used in w3 examples above, create the nested $POST parameters and then use that data how you wish for repeats / inserts.