You can only apply in one category per event edition.
An event organiser may choose to request different personal data for each category. Therefore, once you have started the application process in a certain category, it is no longer possible to change the category you are applying in during the application process.
To apply in a different category, delete your application and start with a new application. Note that if you delete an already approved application, your accreditation will be withdrawn and your new application will have to be reviewed again by the event organiser.