We present XModelerML v3, a multi-level modeling tool that is based on the Flexible Multi-Level Modeling and Execution Language (FMMLx). Multi-level modeling enables the representation of domain knowledge at higher levels of classification, thus reducing conceptual redundancy and improving the integrity, adaptability, and comprehensibility of domain models. This furthermore allows for the specification of domain-specific languages using more generic domain-specific languages, rather than starting from scratch every time. The XModelerML provides a shared representation of model and code and can be used to instantiate and execute models at runtime. With version 3, we now offer the opportunity to specify executable UML diagrams in XModelerML using a specifically developed dialect of FMMLx called UML++. In this demonstration, we showcase how XModelerML v3 integrates multi-level and two-level modeling modes. We describe practical modeling scenarios where this integrated approach offers clear advantages and demonstrate how users can define, execute, and evolve executable models seamlessly within the tool.