I'm experienced with angular 5, typescript, and can build the app with this framework, several examples in my portfolio, slidingplatforms has an editor, dragging and dropping, no collisions between objects and saving data to server. Thinking about how to administer the app, is a SQL Database necessary? I think NoSQL might be a better fit if the the properties on nodes can be changed or not all required. I think maybe using firebase and cloud functions to save and validate the node diagrams being saved.