[Plugin: Page.ly MultiEdit] shadowbox issue

Great plugin I must say, one quick question. I’ve insterted a lightbox like plugin called Shadowbox JS, however my dilemma is I can’t get it to work in the Page.ly MultiEdit content area. When placing rel=”shadowbox” in the href area for the link, it just doesn’t want to read the rel= when working in the editor, but if I place this code in the normal WP editor, it works just fine.

Any solution to this?

https://www.ads-software.com/extend/plugins/pagely-multiedit/