Yes, that's the kind of user interface that I believe should be the basis for modern programming environments. It's also the example I was thinking of when I sa

Yes, that's the kind of user interface that I believe should be the basis for modern programming environments. It's also the example I was thinking of when I said that linked structures are difficult to navigate beyond the few first nodes; a "boxes+arrows" representation just doesn't scale well without a way to structure nodes hierarchically and summarize the state of whole groups of objects. It's been many years since I used it, so it may have evolved to include features for displaying large datasets; however what is needed is something akin to Bret Victor's "Learnable programming" principles, which is more powerful than simply tracing a single deterministic execution path (which is what classic "debugging" is).