PlaceBlock Tool & Promoted Blocks

When to Use

When configuring which blocks appear in the drag-and-drop sidebar, customizing their icons, or understanding the block placement flow.

How PlaceBlock Works

The PlaceBlock tool renders a two-tab sidebar: 1. Promoted tab — curated list of frequently-used blocks with custom icons 2. Other tab — searchable list of all available blocks, organized by category

When the user drags a block from either tab: 1. JavaScript shows drop zones on the page 2. User drops block in desired location 3. AJAX request to DropZones::placeBlock() controller 4. Controller creates block plugin with context mapping 5. If field_sample_value module is installed, fields are auto-populated with sample content 6. Layout is rebuilt via AJAX and rendered inline

Pattern: Configuring Promoted Blocks

Navigate to the content type's Manage Display page, then find the LB+ Promoted Blocks configuration.

Promoted blocks are stored as third-party settings on entity_view_display:

third_party_settings:
  lb_plus:
    promoted_blocks:
      - 'inline_block:basic'
      - 'inline_block:image'
      - 'inline_block:layout_block'
    block_config:
      icon:
        'inline_block:basic': '/modules/contrib/lb_plus/assets/icons/text.svg'

Block Placement in Nested Contexts

When inside a nested layout block, PlaceBlock: - Detects layout_block_uuid from the request - Scopes the block list to the nested context - Merges parent entity's field blocks (any block definition containing field_block:) - Restricts drop zones to the nested layout's regions

DropZones Controller Endpoints

Route	Method	Purpose
`lb_plus.js.place_block`	`placeBlock()`	Place new block from sidebar
`lb_plus.js.move_block`	`moveBlock()`	Move existing block between regions
`lb_plus.js.move_section_drop_zone`	`moveSection()`	Reorder sections
`lb_plus.js.add_section_drop_zone`	`addEmptySection()`	Add new empty section

Sample Content Generation on Placement

When a block is placed, the Dropzones service: 1. Creates block_content entity via createBlockContent() 2. If field_sample_value module exists, calls SampleValueEntityGenerator::populateWithSampleValues() 3. Otherwise, falls back to Drupal core's generateSampleItems() method 4. Block appears on page with realistic placeholder text, images, etc.

Decision

Block Type	Promote?	Reason
Basic (text)	Yes	Most common block
Image	Yes	Frequently needed
Layout Block	Yes	Enables nesting
Custom block types	Yes, if frequently used	Reduces search time
System blocks (breadcrumb, etc.)	Usually no	Rarely used in page building
Views blocks	Selectively	Only if commonly placed

Common Mistakes

Do not promote too many blocks — defeats the purpose of curation. 5-10 is ideal.
Do not forget to configure custom icons for promoted blocks — they help users identify blocks quickly.