How to create and map Airtable records in Softr?

I’ve managed to pass the recordId of an item from my homepage (which lists items from the Airtable “Items” table) to the bid form page/modal (linked to the “Bids” table).

I did this by creating a button that generates a URL with the recordId as a query parameter (e.g., https://xxxxx.softr.app/bid?recordId=recxxxxxxxx), concatenated in an Airtable column.

On the bid form page, I set up a hidden field to capture the recordId from the URL parameter. The form submits fine, and the bid record is created, but the problem is that the “Items” field in the “Bids” table isn’t being populated—so the bid isn’t linked to the correct item. Or to any item at all.

Anyone know how to properly map the recordId to the “Items” field on form submission?