CMB2 Group Map

Originally created for Post Status to associate footnotes with notes, This CMB2 addon allows you to use CMB2 group fields to manage custom post type entries.

You will either need to clone and then run composer install in this plugin’s directory to get the required dependencies, or simply download the compiled zip.

A few details:

To specify the post type destination, add a 'post_type_map' parameter to your group field parameters.
To set the default WordPress post fields (e.g. the post content, title, etc), you need to set the 'id' parameter to the same value as the wp_posts database column name. So for the content, the 'id' parameter would be 'post_content', or for the title, 'post_title'.
To set taxonomy terms for the connected post-type posts, use one of the taxonomy_* field types.

Example

You need to include this library:

require_once( 'cmb2-group-map/cmb2-group-map.php' );

Then setup a CMB2 metabox with a grouped field:

// Standard CMB2 registration.
$cmb = new_cmb2_box( array(
    'id'           => 'footnotes',
    'title'        => 'Footnotes',
    'object_types' => array( 'post' ),
) );
// This is our group field registration. It's mostly standard.
$group_field_id = $cmb->add_field( array(
    'id'            => 'footnotes_ids',
    'type'          => 'group',
    // This is a custom property, and should specify
    // the destination post-type.
    'post_type_map' => 'footnotes',
    'description'   => 'Manage/add connected footnotes',
    'options'       => array(
        'group_title'   => 'Footnote {#}',
        'add_button'    => 'Add New Footnote',
        'remove_button' => 'Remove Footnote',
        'sortable'      => true,
    ),
) );
// by using 'post_title' as the id, this will be the
// value stored to the destination post-type's title field.
$cmb->add_group_field( $group_field_id, array(
    'name' => 'Title',
    'id'   => 'post_title',
    'type' => 'text',
) );
// by using 'post_content' as the id, this will be the
// value stored to the destination post-type's content field.
$cmb->add_group_field( $group_field_id, array(
    'name' => 'Content',
    'id'   => 'post_content',
    'type' => 'textarea_small',
) );
// This field will be stored as post-meta against
// the destination post-type.
$cmb->add_group_field( $group_field_id, array(
    'name' => 'Color meta value',
    'id'   => 'footnote_color',
    'type' => 'colorpicker',
) );
// This field will be stored as category terms
// against the destination post-type.
$cmb->add_group_field( $group_field_id, array(
    'name'     => 'Categories',
    'id'       => 'category',
    'taxonomy' => 'category',
    'type'     => 'taxonomy_multicheck',
) );

Screenshots

Group Field Display
Group pulled from custom-post-type post
Post-select search modal