E. Marten

<p>You need to use WordPress SEO by Yoast (Props to him!)</p>
<p>Adds “More Sitemaps” to your WordPress SEO Settings. If you are using a second WordPress-Installation in a subdirectory, you can now easily add the second Sitemap into the main one.</p>
<p>If you are using a second WordPress-installation in a subdirectory and want it to be fully integrated it into your main site to prevend struggeling with two or more Sitemaps in your Webmastertools,<br />
you can easily integrate more sitemaps into your main one. (sitemap_index.xml)<br />
The Plugin adds your second and third (aso) sitemap into the main sitemap and tooks care about the modification date automatically!</p>
<p>Thanks to Joost de Valk!</p>


IsSiY (Include second Sitemap into Yoast) WordPress SEO Extension

Adds "More Sitemaps" to your Wordpress SEO Settings. Include differen sitemaps to your sitemap_index.xml

Matt Gibbs

<p>WordPress 5.5 includes built-in <a href="https://make.wordpress.org/core/2020/07/22/new-xml-sitemaps-functionality-in-wordpress-5-5/" rel="nofollow ugc">sitemap functionality</a>.</p>
<p>This plugin provides a UI for some of the most common sitemap configuration settings.</p>
<p>NOTE: some plugins (like Yoast SEO) replace core sitemaps with their own version. This plugin only works with core sitemaps.</p>
<h4>Screenshots</h4>
<ul>
<li><a href="https://i.imgur.com/KkDLTvQ.png" rel="nofollow ugc">Settings screen</a></li>
</ul>
<h4>Features</h4>
<ul>
<li>Turn off WP core sitemaps entirely</li>
<li>Exclude all (or specific) post types</li>
<li>Exclude all (or specific) taxonomies</li>
<li>Exclude taxonomy terms by ID</li>
<li>Exclude post items by ID</li>
<li>Exclude all users</li>
</ul>
<h4>Important Links</h4>
<ul>
<li><a href="https://github.com/mgibbs189/sitemap-ui" rel="nofollow ugc">Github <span aria-hidden="true" class="wp-exclude-emoji">→</span></a></li>
</ul>


IsSiY (Include second Sitemap into Yoast) WordPress SEO Extension vs Sitemap UI