While System of Systems (SoS) architectures for large and complex software projects are gaining momentum, the commonly used modeling and tooling approaches are still general-purpose or oriented towards single systems. Developers could benefit from methods and tools that avoid system-centric details in favor of native SoS modeling support. This paper presents a diagram-centric modeling tool with native SoS modeling support. The demonstration will get through the three diagrams & one document used in our approach. The tool is implemented as a plugin for the Eclipse Papyrus modeling tool. The tool is showcased on a SoS to manage the interaction of users with a library. The code of the plugin is freely available via Github (and it will be submitted to the Artifact Evaluation Committee). A video for the accompanying demo can be found at url{https://youtu.be/RT_9SuwAaRA}.