A seller can use SetStoreCategories to modify the category structure of their eBay Store. Store categories can be added, deleted, moved, and renamed with SetStoreCategories. Changes can be made to a single store category or to a list of store categories. Using the API, you can add up to 300 store categories to an eBay Store. Stores support three levels of categories. Use GetStore to retrieve the category structure for your store.
Note: Store categories will not appear in the marketplace user interface unless they contain items.
Items can only be contained within the store's terminal (aka "leaf") categories. A parent category cannot contain items. If adding, moving, or deleting categories displaces items, you must use the ItemDestinationCategoryID input field to specify a destination child category under which the displaced items will be moved. The destination category must have no child categories.
For more information about SetStoreCategories, including input/output fields and samples of the API call structures, refer to the SetStoreCategories reference documentation.