Currently custom tables and their records are permanently associated with an object (i.e., workspace, Epic, Feature, Ideas, etc.) and don't get copied when the parent object is copied and cannot be moved out of an object. It would be best if you can change the parent object of a custom table record (or bulk for that matter would be better), as a function. Most other objects can be moved from one workspace or release to a different one, and given that we cannot do that for custom table is limiting.
The following is a use case. We created an Impacts custom table and associated it with Ideas to allow teams to think through the impacts early on. If that idea is now promoted to an Epic or Feature, that data stays with the idea, and we would like to move that data to the new object the idea is promoted to. This provides visibility of the data in the new object without having to depend on the link back to the Idea and figure things out (and would be a problem if the Idea was promoted again, and thus the original link is broken).