Dunnart is a prototype constraint-based diagram editor. It includes standard diagram editing capabilities, as well as advanced features such as constraint-based geometric placement tools (alignment, distribution, separation, non-overlap, and page containment), automatic object-avoiding poly-line connector routing, and continuous network layout.
Sources here https://github.com/mjwybrow/dunnart/
Dunnart depends only on the Qt cross-platform application and UI framework. All other components are included in the repository.
Dunnart can be built by issuing the following commands:
qmake -recursive -config release dunnart.pro
Seems like the project is dead and other distributions also lack this package: