Design and Super Content
Design content is a default for the content attribute that displays when editing an asset or as content thumbnails or previews when there is no actual content. Once the asset is published, design content is ignored. Design is only supported when used with blocks and slots.
Super content is realistic content that displays when editing an asset. Like design content, super content is only used when editing and is ignored once the asset is published. Super content can be used to show human readable content instead of code, valid URLs and images instead of broken ones, markup that will be resolved at publishing time, or images that don't exist yet. Super content is only supported when used with slots.
Add design content to the asset as a string, using the design attribute.
Add super content to the asset as a string, using the superContent attribute. In this example, the partner uses !!!attribute to identify placeholders they later replace using their API.