This would be a full threading feature, which has been discussed quite a bit in places like: Threaded discussion is ultimately too complex to survive on the public Internet?
When Discourse was created this sort of post structure was intentionally left out in favor of mostly-flat discussions.
So at the moment, posts are only aware of their immediate relationships: “in reply to” and “X replies to this post.”
Data like “this is a reply to post X which is a reply to post Y and post Z is the parent” is not produced… so there’s no concept of a “reply chain” available.