The internal SD to internal SD transfer probably won't work on the Mini (and other pre-Aura-HD devices with only 256MB RAM). That one relies on copying all files into RAM to allow you replacing the internal card on the fly, but it just needs plenty of RAM for that...
For older Kobos with external microsd slot you can use the Magic Memory external variant. But I think the Mini doesn't have external microsd slot either?
So at most you could clone the card using a PC, then resize the data partition with the Magic Memory resize variant.
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