I’m afraid I may be misunderstanding your situation so let me explain what I am doing in an app of my own. As the name of this action indicates, it copies a record from one table to another. The tables are different but the newly copied record will eventually be moved from the Kankaku table to the Archive table, and will have to coexist with the original record. For the most part, I merely copy the individual fields from the the original record as is ([Word] from the Archive table equals [Word] in the Kankaku table, etc.).
However, the [Key] fields (which functions as the “keys” in both tables) cannot be the same; for them to coexist on the same table in the future they must be different. So, here’s what I do:
The action uses the “key” from the Archive table as its base and then adds additional text, making it different (unique). The particularly expression I’m using is for my own needs and isn’t one I would recommend to you but this general approach might be useful to you.
If I have misunderstood your situation and you are trying to do something quite different, my apologies.