title: JavaScript-HTML: Create ComboBox with non-selectable items
body: <p>I would like to create a ComboBox like you can see in the following image</p>
  
  <p><a href="https://i.stack.imgur.com/lYcCo.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/lYcCo.png" alt="Combobox"></a>
  </p>
  
  <p>The Combo/Menu/List should allow some items to be bold (Main Categories), and to have "sub-categories" under each main category. The bold items <strong><em>should not</em></strong> be clickeable or selectable (I guess these items should have value="") ?</p>
  
  <p>Thanks</p>