How to add a new field to a form?

Question

1C

Answer 1

Try clicking on "list" above "date".

Answer 2

You won't be able to do anything.
If the creators of dynamic lists want to allow users to add columns with arbitrary details to the list form, they add a hidden "Link" field. If you stand on this field, then the "Add fields" button becomes active and you can add any details available in the link. Similarly with other reference types - this is how you can select the "Individual" field and add the "TIN" column next to it.