title: Highcharts: Additional legend items to control multiple items
body: <p>I've got a Highcharts bubble chart that displays data for a couple dozen U.S. states. As you'd expect, each state's name appears as a legend item. When the user puts the mouse over a state name, that state's bubble is highlighted in the chart (all other bubbles become partially opaque). Clicking on a state name in the legend toggles that state's bubble on/off.  That's all fine and I'd like to keep all that functionality.</p>
  
  <p>What I want to add is a few legend items that would control a set of multiple state bubbles that I could define.  For example, a "New England" legend item.  Mouseover it and all the New England states (Maine, Vermont, Rhode Island, etc.) would get the highlight effect.  Clicking on "New England" would toggle all of the states in that group on/off.</p>
  
  <p>Anyone have any idea of how this could be done?</p>
  
  <p>Thanks for your attention,</p>