Thanks for your help @davidfor. I think I’ve done it!
I exported all ~7 backed up Bookmark tables to SQL using
DB Browser for SQLite (default settings.)
The only prep that seemed to be necessary (fingers crossed) before importing the SQL dumps:
- Remove the lines before the first INSERT statement, which would cause the transaction to fail.
- Search for "INSERT INTO" in all the SQL dumps and replace it with "INSERT OR IGNORE INTO". (All the DBs had the annotations for the few books I purchased from the Kobo store, and, naturally, those had duplicate BookmarkIDs (the primary key).)
I then loaded the books with heavy annotations onto my Kobo from SD card backups, rather than Calibre, to ensure I ended up with the same edition of the book in the same place, where Kobo could match it up with the appropriate annotations.
I haven’t done much testing but, so far it’s looking good: It didn’t brick my reader, and all the books that I have tried seem to have annotations where there ought to be annotations.
Thanks again @davidfor!
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P.S. As someone who has been an active member of a number of forums over the years, and run a few forums as well, I know how much difference super helpful and knowledgeable people such as yourself make to newbies, and the folks who run the forum — as well as how much time it takes to help all the entitled newbies who come crying for help. So, thanks!