Missing link functionality "rel"

Hi, i don't know if i missed it or if it is missing but i think it is an important tag to have,
When you are using image plugins like light box you need to add a rel="lightbox[image group] to the link, is there any way to implement that or have i missed it (or will it appear in later builds)?

Any help suggestions ect. would be verry apreciated as it is an amazing product.

BR, Peter Nielsen