Support for conceptual modeling

App would be complete for me if I could do true conceptual modeling (multivalue attributes and many-to-many relationships).

Conceptual modeling, by definition, is more abstract than logical modeling. Often, I need a conceptual model to communicate the business rules with nontechnical people. This is also something I teach my students to do. Vertabelo doesn't support conceptual modeling in this way, but if it did it would be a complete full data stack tool.