Use Case diagrams are easy enough to make, but we don’t have an existing sample.
You could also create a diagram that supports UML Activity diagrams. But no one asks for that – most people ask for BPMN or other similar standards. For BPMN see https://gojs.net/latest/extensions/BPMN.html.
I don’t know what the official UML State diagrams are supposed to look like, but I’ve used this sample for designing/analyzing our own code: State Chart
Just as with Use Case diagrams, it’s pretty easy to create Component and Communication and Deployment diagram editors. We can help you.
Thank you so much for your answer. It would be beneficial to have an extension for use case diagram. Is it possible that GoJs team will help with this diagram sample or extension ?