How can I force the description text in my legend to occupy more than one line?

This is basically the same question as asked before.

However, I want to use Categories/Unique values and not Features as my Symbology style, in which case there's no Description button. Even when I change to Features, it seems I can't use multiple lines (I suppose that there's been some changes to this functionality).

How would I go about getting the description/header text across multiple lines?