The cloning worked!

The cloning worked!

I swapped out the old system disk, and swapped in the cloned one to disk 1 / sda position, and it booted to Windows! Then Windows adjusted itself to the Toshiba drive and asked me to reboot afterwards, which I did. All went correctly. And now I've booted to Mint, which seems to work fine (though a little slow, since it can't find the swap partition).

Next I'll carefully look at the System drive using KDEPartition Editor. There should be an extra 1TB (roughly) that I can now allocate to Windows and other things. I won't touch the old System drive until I know that everything's set up the way I want it, and working, and I may need to reinstall Mint in that process.