How do you move existing snapshots to a new device

I made a bad choice when I set up Timeshift on Mint 19 initially. I didn't think it through, and used a partition on the same disc as my root partition instead of a partition on a different disc, which would have been far more sensible as I could then do a simple recovery if my root disc failed.

I can see that it is straightforward enough to copy all the files from the original partition to the new partition, but I am not sure what changes I need to make to any Timeshift configuration files to support this. In the end, I just used setup to change the Timeshift partition identity, and left the original partition and files intact. If possible, I would like to incorporate them into the new configuration.

Any advice on how to achieve this would be welcome, (and perhaps a facility to move partitions added to a future version?). It would also be helpful to add some text to the Timeshift partition selection screen to advise other users not to make this dumb mistake!