In the fields using @Pattern decorator (Regex based validation) is not possible to translate the message parameter. In Stunner there are five classes using that decorator:

• org.kie.workbench.common.stunner.forms.model.ColorPickerFieldDefinition
• org.kie.workbench.common.stunner.bpmn.definition.property.connectors.Priority
• org.kie.workbench.common.stunner.bpmn.definition.property.event.escalation.EscalationRef
• org.kie.workbench.common.stunner.bpmn.definition.property.event.signal.SignalRef
• org.kie.workbench.common.stunner.bpmn.definition.property.task.TaskName