Automatically notify Google & Bing when a sitemap gets updated.

Hello,

Thank you for contacting the support, and sorry for any inconvenience that might have been caused due to that.

You can use this custom filter code to programmatically add/modify your sitemap page and it will automatically notify the search engines as long as you turn on the Ping Search Engines settings:

add_filter( 'rank_math/sitemap/index', function( $xml ) {
	$xml .= '
		<sitemap>
			<loc>http://example.com/new-sitemap.xml</loc>
			<lastmod>2020-09-14T20:34:15+00:00</lastmod>
		</sitemap>';
		return $xml;
}, 11 );

You may refer to this article: https://rankmath.com/kb/filters-hooks-api-developer/#18-filter-to-add-external-sitemap-to-the-rank-math-sitemap

Hope that helps and please do not hesitate to let us know if you need our assistance with anything else.