How to add class on Widget Title

Two approaches:

1. Don’t bother

   Just target .widget.{dynamic-class} h3 instead

2. Use %2$s

   I don’t know if this will work, but try:

   'before_title' => '<h3 class="%2$s">'

But personally, I’d go with the former option. You’ve already got a unique class name; just leverage the element hierarchy to apply styles selectively.