A block with type HEADING_3. Used for small headings.
Unique identifier for this block.
HEADING_3 Groups related blocks together. For standalone blocks, use the block's own uuid. For child blocks (e.g., dropdown options, multiple choice options), use the parent block's uuid so all children share the same groupUuid.
HEADING_3 Payload for HEADING_3 block type. Used for H3 headings.