I believe I am beginning to understand how the metadata is handled in Calibre.
It looks like the metadata tags are stored in three separate places. The main Calibre database, the EPUB file itself, and the external OPF file.(Sometimes it pays to read the manual
).
Now that I understand this I've found a solution (albeit a clunky one) -
Step one – Make a new Calibre library, and add newly generated EPUB file(s) to the library.
Step two – Open the path to the new EPUB file(s) and remove the metadata.opf file(s).
Step three – Switch to the original library, and locate the original EPUB file(s).
Step four – Open the path to the original EPUB file, and copy the metadata.opf file(s) to the corresponding folder(s) in the new library.
Step five – Switch back to the new library, and restore the database.
Step six – Repeat steps two through five as needed.
The modify EPUB plug-in appears to be able to write to the metadata.opf file, but not read from it (still very useful in other ways, though).
FWIW, I would love to see a plug-in that reads the metadata embedded in the EPUB file
and the metadata.opf file and allows one to compare the two, make changes in either location, synchronize the data (in either direction), and update the Calibre database.
I've considered using Sigil to edit the existing EPUB files, but in this instance, I decided it would be easier to create a new structure, rather than attempt to patch the old one.
I'd like to thank you again for your response, and your assistance. You pointed me in the right direction, and as a result, I've learned a little bit more about the EPUB format.
