Also, if you do not want every book to be queued for an automatic metadata.opf backup, simply run the Job Spy GUI Tool named "Purge metadata.opf Backup Queue".
For actions that cause that to occur without restarting Calibre, you can click that Tool immediately. For others, such as changing Custom Columns in Preferences that requires a restart of Calibre, you can click that Tool as soon as Calibre restarts. A few might slip through, but better a few than tens of thousands of undesired metadata.opf updates that you find to be unnecessary and undesirable.
https://www.mobileread.com/forums/sho...d.php?t=269911
DaltonST