Yes, Adding items to the relationship tab is now supported. (as of 8.0)
The Wiki will be updated shortly but here’s the basic notes on this.
The relationship tab support will follow the same basic design as grid and workflow items.
The features supported:
item.relationships -- A list of relationships
item.relationships.addRelated({ RELATED: target, TYPE: typeStr, DIRECTION: dir, DESCRIPTION: desc }) – Adds relationship to list
item.relationships.addRelated(target, typeStr, dir, desc) – Adds relationship to list
dir is optional, and defaults to Unidirectional. Will be bidirectional if dir is 2 or "bidirectional" (case insensitive)
desc is optional, and defaults to blank
item.relationships[i] has the following properties:
item.relationships[i].id – DMS ID of target item
item.relationships[i].descriptor – Descriptor of target item
item.relationships[i].item – Target item
item.relationships[i].item.FIELD – Field on target item
item.relationships[i].type – Relationship type name
item.relationships[i].direction – One of “Unidirectional” or “Bidirectional”
item.relationships[i].description – Relationship type description
item.relationships[i].setRelationshipType(typeStr) – Sets the relationship type to “typeStr” (or throws an error if “typeStr” is not valid)
item.relationships[i].setDescription(desc) – Sets the relationship description to “desc”
item.relationships[i].remove() – Removes relationship i from the list