I have been using https://www.yworks.com/products/yed https://www.yworks.com/products/yed for years. You can import a c4 palette probably. I do not really stick

I have been using https://www.yworks.com/products/yed https://www.yworks.com/products/yed for years. You can import a c4 palette probably. I do not really stick to specific shapes but use what makes sense for the context.