Thank you for reaching out, and I apologize for the inconvenience you are experiencing.
Please note that within SP Page Builder’s Dynamic Content system, it is designed to allow only one Index page and one Details page per content type, and this is not a temporary limitation—it will always work this way.
If you would like to create a new Index page, you will need to completely remove the existing one first. Please ensure it is fully deleted (including removing it from the Trash and clearing any related cache) before attempting to create a new Index page.
Thank you for your understanding. If you need any further assistance, please feel free to contact us.
Kind regards