[Sirtel]

I do what BetterRed does, and copy the original to the book's data folder before editing. I don't particularly like multiple separate libraries and want to keep their number as low as possible (currently I have three - my main library, one for interacting with my Kobos and one for deDRMing Kindle books, where I keep the Amazon originals). So I edit in my main library. I use the calibre editor, so nothing is done outside the library.

But I'd like to use multiple calibre instances too sometimes, on different libraries. Yes, it can be done via a second Windows user account, but that's a pain (you must give the second account permissions to access your main account).

Yes, I know it could be dangerous.