Magnolia 5.6 reached end of life on June 25, 2020. This branch is no longer supported, see End-of-life policy.
To create a custom workflow process it's highly recommend that you use the Eclipse BPMN2 Modeler plugin available in the Eclipse marketplace.
You can implement a simple 4-eye publishing workflow with tasks. You don't need the Workflow module or jBPM unless your workflow is more complex, involving three participants or rejection.