Hi @refreshingdesign
Good question.
To modify the DOM without reloading the page, you will need to write some custom jQuery on the edit screen.
You could either use an AJAX call to allow PHP to return the choices, or just look at the text inputs to generate the choices.
To add a script tag to the edit screen, use the acf/input/admin_head action.
You find some examples of this action on the docs (actions) page.
Cheers
E
