Add custom sitemap to sitemap index

I have different sections on my site and have different sitemaps for them. I would like to know if there is a way to add those sitemaps to the sitemap-index.xml file generated by the WordPress SEO plugin.

I can always submit my custom sitemaps directly to search engines, however, it could be a great feature to be able to add more sitemaps to the sitemap index and not having to to be able to submit multiple sitemaps manually to different search engines.

https://www.ads-software.com/plugins/wordpress-seo/