In a new Drupal 8 build that I am working on, there is a use case for some menu items to have an abbreviation underneath. I wanted to create a content editor friendly way of achieving this in the Drupal menu admin UI. Since I have already implemented the Drupal 8 Link Attributes widget module, I got to thinking that perhaps I could extend the module to handle these abbreviations.
Extending the Link Attributes widget
I was happy to discover that Link Attributes can be extended to any kind of additional HTML attribute you might need for your menu. I came up with the idea that if I could add a new field for the abbreviation, I could turn it into an HTML data attribute for a menu item and then output it with a little jQuery.
There are two pieces to extending the widget within a custom module,