I would really love to see the ability to implement HTML tooltips or text pop-ups on mouseover in the editor. For blogs, this can be a critical feature to explain references quickly as an aside to newer readers while moving on so that others don’t need to stop to read an explanation. I even had readers ask for this to be implemented! After some research, I learned how it could be done via HTML, but HTML blocks don’t render in emails, so I would have to release the article without this feature, then edit the article to replace the entire text with HTML blocks to incorporate this feature.