If your custom layouts area is getting cluttered and you want to remove layouts you no longer need, you can delete them.
To delete a saved layout from the My Layouts section, go to Layouts and select My Layouts from the dropdown menu, then hover over the layout you want to remove until you see the trash can. Click the trash can icon to delete the layout from BookWright.
This won't affect any pages in your book which currently use that layout--it simply removes the saved layout from the My Layouts list (and from your computer).