Modelio JDL Studio is a Modelio module created by Softeam/Modeliosoft that allows Modelio users to design a JDL (JHipster Domain Language) data model diagram and then to generate from it a JDL file for entities and their relationships.
The Modelio JDL Studio is available for the Modelio Open Source and is compatible with the version: 4.0 which can be downloaded for free here.
The full documentation including both the installation guide and the user guide is available at Github Wiki and Redmine Wiki.