Form layout / Multiple values / Add another item button

I’ve created my content types, fields and so on and get my desired fields on my edit forms as you would expect, however, some of the data held will only ever have a single value but some will have multiple values (for example names, some have a single first name, others may have multiple first names) yet the form renders an empty box as well as the “Add another item” button giving a redundant box on the form, when you scale this over several fields that’s a lot of redundant boxes on the form.

So I can keep the form clean and friendly for my non-technical content editors, how can I get the form to render with just a single box and the button?

I’m happy to dig into code, but guessing this sort of UI control should be available somewhere.

I’m currently using the default Seven theme, but will be writing a custom theme later on once the data mapping phase is complete.

Drupal version: