Frankly I’m not even sure that there’s a way to complete this task, but am sending this question out to the world.
When I got my first Kindle in 2007, I briefly subscribed to a magazine and a newspaper that were delivered to the device. I preferred reading them elsewhere and promptly cancelled the subscriptions. Both magazine and newspaper still show as Inactive Subscriptions in the Amazon website’s Content and Devices. There is only one box to the left of each periodical. There are four options, none of which allows deleting the listing as one can easily do with a book.
I have called Kindle’s experts over the years. They say it can’t be done.