Thank you for the introducing the timeline. It gives you a great overview about what happened in a post.
I would suggest to list the full urls of the duplicate targets when the dupe list is edited or when a post is closed as a duplicate.
Currently, when the duplicate list is edited, all we see is:
When a post is closed, it merely gives the "Duplicate" reason, and doesn't include the dupe targets:
Could we display links/urls here?