How to display a complex value that depends on multiple meta fields?

My recommendation for those complex use cases is to register a rest field. Here is the demo code:

// Create a function to build rest field value.
function yourprefix_get_rest_field( $post_id ) {
	return 'calculate field value from $post_id';
}

// Register a rest field.
add_action( 'rest_api_init', function () {
  register_rest_field(
    'post',
    'your_rest_field_name',
    array(
      'get_callback' => function ( $post_array ) {
        return yourprefix_get_rest_field( $post_array['id'] );
      },
      'schema'       => array(
        'type' => 'string',
      ),
    )
  );
});

// Display the content of the rest field.
add_filter( 'meta_field_block_get_block_content', function ( $content, $attributes, $block, $post_id ) {
  $field_name = $attributes['fieldName'] ?? '';

  if ( 'your_rest_field_name' === $field_name ) {
    return yourprefix_get_rest_field( $post_id );
  }

  return $content;
}, 10, 4);