link to documents jbpm-docs:

#sect_deployment_descriptors[Deployment Descriptors] chapter of the jBPM Administration and Configuration Guide.

[_sec.designer.workitems] [_ch.designer]:
If you’re using Designer, then this means creating a MVEL based definition and adding the definition in Designer itself. A description of this can be found in the [_sec.designer.workitems] section in the [_ch.designer] chapter. Once this is done, a new service node will appear on the BPMN 2.0 palette.

[_sec.eclipse.task_nodes] [_ch.eclipse_bpmn_plugin]:
If you’re using the Eclipse BPMN 2.0 modeler plugin (which can be found here), then you’ll can modify the BPMN2 <task> or <task>-type element to work with WorkItemHandler implementations. See the [_sec.eclipse.task_nodes] section in the [_ch.eclipse_bpmn_plugin] chapter.