functions.php

<?php

add_action( 'bcn_after_fill', 'project_rebuild_breadcrumb' );
/**
 * Rebuild the breadcrumb created by Breadcrumb NavXT.
 *
 * @param bcn_breadcrumb_trail $breadcrumb Instance of the currently active breadcrumb trail.
 */
function project_rebuild_breadcrumbs( $breadcrumb ) {

	if ( ! is_singular( [ 'case-studies', 'articles', 'presentations', 'papers-reports', 'creative-portfolio' ] ) ) {
		return;
	}
	
  	// Default breadcrumb template.
  	$breadcrumb_template = '<span class="breadcrumb-link-wrap" itemprop="itemListElement" itemscope="" itemtype="https://schema.org/ListItem" property="itemListElement" typeof="ListItem"><a itemprop="item" property="item" typeof="WebPage" title="Go to %title%." href="%link%" class="%type%"><span property="name">%htitle%</span></a><meta property="position" content="%position%"></span>';
  
	/**
	 * Store the first and last breadcrumbs, we're rebuilding the middle part.
	 */
	$breadcrumb_root = reset( $breadcrumb->breadcrumbs );
	$breadcrumb_end  = end( $breadcrumb->breadcrumbs );

	/**
	 * Build our custom Knowledge breadcrumb.
	 */
	$knowledge_page            = get_page_by_path( 'knowledge' );
	$breadcrumb_title          = __( 'Knowledge', 'project' );
	$breadcrumb_link           = get_the_permalink( $knowledge_page->ID );
	$knowledge_item_breadcrumb = new bcn_breadcrumb( $breadcrumb_title, $breadcrumb_template, [], $breadcrumb_link, $knowledge_page->ID );

	/**
	 * Update the Breadcrumb NavXT object.
	 */
	$breadcrumb->breadcrumbs = [
		$breadcrumb_root,
		$knowledge_item_breadcrumb,
		$breadcrumb_end,
	];
}
}