In Modelio diagrams, elements are created using the icons in the palette on the left of the diagram.
All Modelio diagrams include the model expert feature, which provides real-time assistance when you are creating elements in diagrams.
Examples:
Creating a package in a class in a class diagram – forbidden
If you try to create an unauthorized element (in this example, if you try to create a package (1) inside a class), the model expert highlights the concerned element in red (2), indicating that the creation operation you are attempting is not allowed.
Creating an attribute in a class in a class diagram – allowed
If you try to create an authorized element (in this example, if you try to create an attribute (3) inside a class), the model expert highlights the concerned element in green (4), indicating that the creation operation you are attempting is allowed.