Just for context, my experience with Camunda so far is just reading the documentation and building some samples.
In reading the "Fluent Builder API" I found it remarkable (in an unfortunate way) that an api for potentially building hierarchical models is structured linearly. I noticed the attempt to indent some calls differently from others to try to illustrate the hierarchy, but that doesn't seem very effective to me.
I would have expected an api for building hierarchical models would also be hierarchical. I suppose if you're restricted to Java 7 there's not much you can do, but if this api could be designed with Java 8 in mind, I would like to see "sub" components defined by lambda arguments, allowing a true hierarchical structure.