The built-in graphviz implementation does not seem to allow hidden connections in some diagrams. Is this intended or still missing?
It's indeed a bug that has just been fixed in last beta http://beta.plantuml.net/plantuml.jar
Tell us if it's not working for you and please go on in publish issue report about this built-in graphviz implementation.
the jdot is the internal implementation of graphviz.
Note that the directive has been renamed to !pragma graphviz_dot smetana
We do not use "jdot" name anymore now because there are some others projects using this code name and this is putting some more confusion to something already complex :-)
In fact the main goal, is for some infrastructure where Graphviz is missing or just to avoid to install Graphviz (and avoid also dependences with Graphviz).
Note that there are another long term goal we did not mention yet: once smetana will be completely working (don't expect that before 3 to 6 years!), our intention is to refactor it and to directly call internal GraphViz methods (so, in Java, in that long term future) that will allow us to overcome some limitations we have right now because we must use the "dot" language as intermediate (since we generate an intermediate "dot" file)
GraphViz is a treasure of powerfull algorithms that will allow us to generate better diagrams.
But don't hold your breath !