| CommentIcon | An icon which allows the user to add comment text to a block. |
| Icon | The abstract icon class. Icons are visual elements that live in the top-start corner of the block. Usually they provide more "meta" information about a block (such as warnings or comments) as opposed to fields, which provide "actual" information, related to how a block functions. |
| IconType | Defines the type of an icon, so that it can be retrieved from block.getIcon |
| MutatorIcon | An icon that allows the user to change the shape of the block. |
| WarningIcon | An icon that warns the user that something is wrong with their block. |