Configurable layout plugin

example.layouts.yml

example_image:
  label: 'Image'
  class: '\Drupal\example\Plugin\Layout\LayoutDefaultConfig'
  path: layouts/example--image
  template: example--image
  category: 'Columns: 1'
  icon: icon-image.svg

LayoutDefaultConfig.php

<?php

namespace Drupal\example\Plugin\Layout;

use Drupal\Core\Layout\LayoutDefault;
use Drupal\Core\Plugin\PluginFormInterface;
use Drupal\Core\Form\FormStateInterface;

/**
 * Provides a default class for configurable Layout plugins.
 */
class LayoutDefaultConfig extends LayoutDefault implements PluginFormInterface {

  /**
   * {@inheritdoc}
   */
  public function defaultConfiguration() {
    return [];
  }

  /**
   * {@inheritdoc}
   */
  public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
    return $form;
  }

  /**
   * {@inheritdoc}
   */
  public function validateConfigurationForm(array &$form, FormStateInterface $form_state) {}

  /**
   * {@inheritdoc}
   */
  public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {}

}