Use shortcode to display Table Of Content Plus on WPRichSnippets enabled posts https://wprichsnippets.com/doc/table-content-plus/

wprs_add_toc.php

<?php

//* Do NOT include the opening php tag shown above. Copy the code shown below.

add_filter('wprs_box', 'wprs_add_toc_4321');
/*
	Use shortcode to display Table Of Content
	This is a simple fix for Table Of Content Plus Plugin
*/
function wprs_add_toc_4321($box) {
		
	if ( shortcode_exists( 'toc' ) ) {
		$toc = do_shortcode('[toc wrapping="left"]');
		$box = $box .$toc; 
	}
		
	return $box;
}