Its also a good idea to back up Calibres configuration settings, the location can be found via Preferences->Miscellaneous->Open Calibre configuration directory.
I'm not sure if you could restore this directory in the event of having to do a Fresh Install of Calibre (e.g. because you lost the system drive).
However a backup of it can at least tell you what plug-ins you had, give some clues as to changes you made in preferences etc.
BR
|