This plugin allows Posts 2 Posts connections to be created and imported using Really Simple CSV Importer. This WordPress plugin requires Really Simple CSV Importer (https://wordpress.org/plugins/really-simple-csv-importer/) and Posts 2 Posts (https://wordpress.org/support/view/plugin-reviews/posts-to-posts)

rscsv-p2p-plugin.php

<?php 
/*
-------------------------------------------------------
Plugin Name: RSCSV/Posts 2 Posts
Description: Connect imported posts using Posts 2 Posts connections
Author: Chris Weissenberger, Aleksandr Beliaev
Version: 1.3
*/
add_filter('really_simple_csv_importer_post_saved', function($post) {
    if (is_object($post)) {
        //connected posts' slugs are delimited with ';' and imported as custom field in separate column with 'ministries_prayers' header
        global $wpdb;
        $ministries = $post->ministries_prayers;
        $missionaries = $post->missionaries_prayers;
        if (isset($ministries)) {
            $min_slugs = explode(';',$ministries);
            foreach ($min_slugs as $min_slug) {
                $min_slug = preg_replace('/\./','-', $min_slug);
                $min_id = $wpdb->get_var("SELECT ID FROM $wpdb->posts WHERE post_name = '$min_slug' AND post_type = 'ministries'"); 
                // $debugtext = $debugtext.' // found spec slug:'.$min_slug.'; post ID: '.$h->postid().'; spec id:'.$min_id;
                // $h->add_meta('ministries_prayers', $debugtext, true);
                if ($min_id) {
                    // echo "<script>console.log('Post ID: ".$post['ID']."');</script>";
                    p2p_type( 'ministries_to_prayers' )->connect( $min_id, $post->ID, array(
                        'date' => current_time('mysql')
                    ) );
                }
            }
        }
        // connected posts' slugs are delimited with ';' and imported as custom field in separate column with 'missionaries_prayers' header
        if (isset($missionaries)) {
            $miss_slugs = explode(';',$missionaries);
            foreach ($miss_slugs as $miss_slug) {
                $miss_slug = preg_replace('/\./','-', $miss_slug);
                $miss_id = $wpdb->get_var("SELECT ID FROM $wpdb->posts WHERE post_name = '$miss_slug' AND post_type = 'missionaries'"); 
                // $debugtext = $debugtext.' // found spec slug:'.$miss_slug.'; post ID: '.$h->postid().'; spec id:'.$miss_id;
                // $h->add_meta('missionaries_prayers', $debugtext, true);
                if ($miss_id) {
                    p2p_type( 'missionaries_to_prayers' )->connect( $miss_id, $post->ID, array(
                        'date' => current_time('mysql')
                    ) );
                }
            }
        }
    }
});