Inject into TinyMCE Inline Link Query

I think it doesn’t use the REST API, but it has an AJAX handler that might have a filter.

Ajax handler is wp_ajax_wp_link_ajax(), but no immediate filter there. You could use ‘wp_link_query’ filter, which passes an array of post data. For API endpoints you’d need to compose fake post data. I think post $ID = 0 should be OK for all, but untested.

Thanks! I was able to get it to work as using the wp_link_query filter. I’ve provided an example below that may not make much sense out of context.

/**
 * Add Endpoints to Inline Linking Tool
 * 
 * @param Array $results
 * @param Array $query
 * 
 * @return Array $results
 */
function prefix_add_endpoints_to_inline_links( $results, $query ) {
	
	$endpoints		= prefix_get_endpoints();	// Array of endpoint data keyed by group then by endpoint
	$possibilities	= array();
	
	foreach( $endpoints as $group => $groupdata ) {
		foreach( $groupdata as $endpoint => $epdata ) {
			
			if( ! $epdata['show_in_nav'] ) { // Custom flag to skip showing endpoint
				continue;
				
			// Search Endpoint Nicename against query
			} else if( false !== stripos( $epdata['nicename'], $query['s'] ) ) {
			
				$possibilities[] = array(
					'ID'		=> 0,
					'title'		=> $epdata['nicename'],
					'permalink' => prefix_endpoint_url( $endpoint, $group ),	// Grab the endpoint URL
					'info'		=> 'EP ' . ucfirst( $group ),
				);
				
			}
			
		}
	}
	
	$results = array_merge( $results, $possibilities );
	array_multisort( array_column( $results, 'title' ), SORT_ASC, $results );
	
	return $results;
	
}
add_filter( 'wp_link_query', 'prefix_add_endpoints_to_inline_links', 10, 2 );

Thanks again!