This feature exists for Branch Lifecycle already. This is not exactly what you are suggesting above but a Branch Lifecycle is required to have the object on a Merge Request.
In Developer Studio, use the option for Branch Lifecycles and then the option to Search Object History. Any Branch Lifecycle listed would have links to Associated Merge Requests and task design details etc…
In the Search Object History application, the Notes field is Available Hidden. If the previous developer wrote Notes on their Branch Lifecycle, they would be visible there. Showing that column is stored as part of your user preferences so it should be shown for you once you move that toggle to Show