Can I Change my Categories on Amazon KDP After my Books are Published?
Sometime after publishing your book you may decide to change the category. You can do this easily by logging into your Amazon KDP account.
Find the book you want to update the categories on then click the ... on the right hand side and pick "Edit print book details".
Scroll towards the bottom of that page to Categories section. If you had already picked 2 initially, you will need to uncheck one or both in order to change your categories.
You can also email Amazon KDP and ask if they could add your book to more than the 2 categories picked, include the category you would like your book added to. They will reply and let you know if they did or not.