Not sure if this will work for your use case, but I think this tool is super cool so I'll rep it: PlantUML is a tool that generates diagrams based on a markup language.

Some key features include UML modeling with object-model diagrams, code frame generation for C, C++ and Java, model import from Rational Rose, and integration with third-party requirements ...

This lab designs ER diagrams in UML notation. The AutoER auto-grading software on PrairieLearn is used to design and mark your UML diagrams. It is also valuable to learn how to use commercial UML ...