Ah, I've seen that happen - actually I wanted to change a variable to use a different font not the regular body font, so that's how I figured out how it is.
Insert a variable, and then in the XML editor highlight JUST the variable. The available options in the Styles window change to show styles that are applicable to variables. (Press F12 if you don't have the Styles window open.) The style, or class, that is most likely what you have is
Madcap:variable, which you should see at the top of the Style window. To check what bits have changed from the default, click
Edit style.
Styles for variables are just like other styles, in that there's a parent class (e.g. <p>) to which you can add sub-classes. If you want to have some variable sets in one font and others just in the default font for the paragraph the variable has been inserted into, you might want to edit
Madcap:variable so that all the values are "default", and you can add another sub-class (in my case I added
Madcap:variable.UI) and apply various attributes such as a different font, italics, bold, that kind of thing. To add another style, at the top of the Styles window, when your variable is highlighted click Edit style. Add the name of the sub-class (for mine I just added "UI", not the whole thing). A new style is added to the stylesheet and applied to the variable. To edit the style, click Edit style to go to the stylesheet and fiddle around with the attributes.
There, that should do it for you. Let me know if it doesn't.
