Hi @Kane T , unfortunately this is just a limitation of the platform. It's not possible to override the styles of the ".identityBanner" or the width of the "vertical-lightbox-container" using custom CSS. What other users have done is create their own front-end and then pass the values through for authentication. I know it's not what you're looking for but that seems to be the best option. Please let me know if you have any questions and I can help you further. If this answer helps you please mark "Accept Answer" so other users can reference it.
Thank you,
James