In other tools, this is hooked up to something like F4. Those tools are able to show a tree view of the type hierarchy (superclasses and subclasses). We may have to expose this info in a vscode selection list (https://code.visualstudio.com/docs/extensionAPI/vscode-api#_window), so would need to flatten it somehow.