Nested objects are flattened using dot notation — for example, address: {city, state} becomes two columns: address.city and address.state.
Arrays of simple values are joined with a semicolon in one cell; arrays of objects are kept as a JSON string within the cell since flattening them further would be ambiguous.
Yes — semicolon, tab, and pipe are available alongside comma, useful for CSV files exported from regions or tools that use a different delimiter convention.