you are correct, the class designer does not support records. see this thread for status:
Visual Studio class designer don't support records from C#
hoshik
35
Reputation points
when I try to display record on the visual studio class diagram, I get an error
Also, the class diagram does not recognize the primary constructor in record as public properties
Error:
One or more selected elements cannot be added to the class diagram. Check the code for errors and note that you can only add types in the scope: — types specified in the project that contain this schema, — public types defined in the assembly referenced; — public types specified in a successfully created project that is referenced; — the types specified in the imported shared project;