If you take a look at the Custom Forms demo app, you’ll see an example of a working table being used.
For your specific use case - creating a parent record, followed by a number of associated child records, my general approach is:
- Start by setting a user specific UUID value in the working table, using the Unique Identifier special value
- Build the initial form out on top of the working table, using a details screen with all input components writing to user specific columns
- On initial submit, add a row to the master (parent) table, using the generated UUID as a record ID
- Reload the same screen (show new screen->this item), and present the secondary form for adding child records.
- On submit, write the same UUID value in a “parent ID” column to establish the link from the child record to the parent.
- Rinse, lather, repeat for as many child records as are required.
An alternative to the show new screen->this item step can be to stay on the same screen and use visibility conditions to hide/show components based on the stage in the process. But that can get a bit cumbersome and difficult to manage.