How to create a modal sub-form to add a new related record inside a main form?

Hi! I’m working on Softr with Airtable and have two relational tables: “incarichi” and “studi notarili”, connected through multiple lookup fields.

I need to build a form for “incarichi” in Softr where the user selects a notary office from an existing list. If the notary is not in the list, I need the form to offer an option to add a new notary office on the fly.

The key requirement is this: I don’t just need to insert a single missing field. I need a modal sub-form that opens inside the main “incarichi” form and allows me to create a full new record in the “studi notarili” table (which contains many fields, not just the name). After saving, the new record should become selectable in the original field.

Looking for guidance on how to implement this, or to confirm whether this behavior is currently supported. Thanks!