Is it possible to format the font used for custom navigation links?

Support
2

Use CSS for this.


E.g.:

/* Add a fontwesome icon*/
a[href="/category/assistenza"]:before {
  display: inline-block;
  font-family: FontAwesome;
  font-style: normal;
  font-weight: normal;
  line-height: 1;
  content: "\f0fa";
  margin-right: 3px;
}
/*Change background only for my custom button*/
a[href="/category/assistenza"] {
    background: #0000B3 !important;
    color: #fff !important;
    border-radius: 15px;
}

You can use Google font to change characters if you want.
Or you can simply change the color (e.g red) and add a font-style (e.g italic)

color: red !important
font-style: italic !important;

So, you can do everything with CSS

In the same stylesheet where is your code, in the CSS tab.

OFF-topic:
Great avatar BTW, just finished to watch Ash Vs Evil Dead!