With the help of this module, you can add/remove the URLs from the sitemap, you can add the custom URLs in sitemap xml.

Magento 2 XML Sitemap Splitter allows you to generate and splits your XML sitemap into multiple sitemaps for better crawling and ranking in search engines.

Magento 2 HTML Sitemap helps you provide your visitors with a convenient overview of your whole site structure. Also, it helps search engines better crawl and index your site pages.