Hi Andee,
When you open a shared link to a document there is no undo history. If you come upon someone midstream in their work on a document, there may be quite a bit of undo history, but certain operations are currently not undoable, and the undo history is cleared when the user brings one of those about. (We’re currently working on making all operations undoable.)
CODAP emits an anonymous log stream. Some projects have made use of that, but I haven’t seen anything come from it. I think it would be a bit of work for Concord and for a collaborator to make the log stream fully usable for research.
Bill