I’m trying to test drive my first process and I want to run a shell script.
I need to set a “flowable:type” to “shell” on a service task
(http://www.flowable.org/docs/userguide/index.html#bpmnShellTask).
How does one do it in flowable modeller?
The “shell” type isn’t implemented in the web modeler, currently. In part, because calling out that way is a very unpredictable operation (sandboxing of JVM etc etc), and not one we’d encourage.
If you or anyone wants to add it, we’d take a pull request - it’s a nice little piece of work to learn more about Flowable 
Cheers
Paul.