Default Value - pre propulate - filter ?

Hi,

I think normalize filter or field_meta filter both works. However, using normalize filter seems to be better.

But why don't you just use a condition check when defined meta boxes? I think it's faster. Something like this:

add_filter( 'rwmb_meta_boxes', function( $meta_boxes ) {
    $field = array(
        'id' => 'test',
        'type' => 'text',
        'std' => 'Default value',
    );
    if ( is_admin() ) {
        $post_id = isset( $_GET['post'] ) ? $_GET['post'] : ( isset( $_POST['post_ID'] ) ? $_POST['post_ID'] : false );
        if ( 1 == $post_id ) {
            $field['std'] = 'Another default value';
        }
    }
    $meta_boxes[] = array(
        // ...
        'fields' => array(
            $field,
            // ...
        ),
    );
    return $meta_boxes;
} );

Or you can filter directly to rwmb_meta_boxes to change the std value of a field:

add_filter( 'rwmb_meta_boxes', function( $meta_boxes ) {
    if ( is_admin() ) {
        $post_id = isset( $_GET['post'] ) ? $_GET['post'] : ( isset( $_POST['post_ID'] ) ? $_POST['post_ID'] : false );
        if ( 1 == $post_id ) {
            $meta_boxes['fields'][0]['std'] = 'Another default value'; // First field
        }
    }
    return $meta_boxes;
}, 9999 ); // High priority to make sure this function run last