User friendly way to add related rows in separate tables at the same time?

Suppose I have databases for Deals and Deliverables, where each Deal is associated with some number of Deliverables. I’m wondering if there’s a simple way that users within the doc can submit the details of a Deal and it’s associated Deliverables in one step.

What seemed obvious to me would be to create a Form view for the Deals database where the property corresponding to the associated Deliverables is displayed as a subtable where the Deliverables can be added. Unfortunately, subtables do not appear to be supported within the Form view.

Any suggestions would be appreciated.

Why not combine the two tables?

Similar topic: Besides Automations, is there a way to compose the data submitted through a flat form into structured (multi-table) rows?

The above is based on an approach of presenting a form (either an actual form which when submitted creates a row, or some Detail view of a table) to the user to ingest all the necessary data into a row in some intermediate table. Then another step (such as a button or an automation) would pull the created row from the intermediate table, and use the data to create the appropriate rows in other tables (and optionally delete the intermediate row).