Extend Display Builder with source plugins

Source plugins are managed by UI Patterns 2. See UI Patterns 2 documentation.

Source plugin for slots

A source plugin targetingslot prop type:

namespace Drupal\my_module\Plugin\UiPatterns\Source;

use Drupal\Core\StringTranslation\TranslatableMarkup;
use Drupal\ui_patterns\Attribute\Source;
use Drupal\ui_patterns\SourcePluginBase;

#[Source(
  id: 'wysiwyg',
  label: new TranslatableMarkup('My slot source'),
  prop_types: ['slot']
)]
class WysiwygWidget extends SourcePluginBase {
}

.. will show up in the Block Library panel:

🚧 2025-07-01: "[Entity] ➜ [Field]" will be flatten. #3529260

Source configuration from PluginSettingsInterface::settingsForm() is available in the contextual sidebar. For example:

🚧 2025-07-01: Sidebar title is not dynamic yet #3531253

Source plugins for props

They are displayed in the component form managed by UI Patterns 2. Display Builder is doing nothing specific here.