Stumped on a low code / no code solution - forms with multiple tables associated

Question

So we build applications in the legal space; we are venturing into a new area and I know it will change a lot in the early days so I'm leaning towards a low code / no code solution to start so we can iron out all the mistakes before the app build.

I'm stumped though because what I need is:

1. The ability to publish a form that customers can fill in
2. The ability to add data to a second table from that form (i.e. we'd have the first table called 'case' and that will have case information. But then we need the ability to add multiple family members and multiple assets. These would ideally be in that same form.)
3. The ability to build an internal app pointing at that data

Ideally, the ability to use that form for pre-populating/editing data - perhaps using URL parameters

I'm really getting stuck on point 2 - I could do it as conditional fields so "name the number of assets you have" and then you can add asset 1 name, asset 1 amount, asset 2 name, and asset 2 amount. But then I'd need to add fields for about 30 assets.

I've tried retool - but their forms don't have any mechanism for adding row entries into a second table. I can't do the conditional fields either because the event handlers on working on submission.

I've tried airtable - but it has to be flat - one form to one table.

I've tried coda - same problem.

I'm a bit stumped on what to use. I hope I've explained the problem well enough!

Coda, airtable, retool so far.