@Taomyn gave a good idea which I think was to delete the database manually after getting its path from Database screen. I think that’s what I usually do (more or less – sometimes I “delete” by renaming, just to keep the old one around in case I need it). There was (maybe still is) a problem where the database isn’t deleted when the job gets deleted, basically just wasting some space and leaving clutter to confuse me…
Although I didn’t see your exact results, I did see the Delete button not be available for use (grey not blue), and I’m not sure what that’s about. I have a somewhat odd installation, so maybe that’s related somehow.
The other surprise came in Google Drive testing, where using drive.google.com to delete all files from the backup folder left them still listed to Duplicati, which complained they weren’t in its deleted local database. They were not visible from a different client (Cyberduck), but available to Duplicati, which could Recreate.
Files: trash possibly explains what’s going on, saying files in the trash are still listed. Maybe available too?
Your situation sounds like the opposite, where you managed to make the files disappear, but the database somehow remained (counter-argument to that is your comment about seeing a new 120kb file created…).
The export/import/adjust-various-things is a reasonable option, although it has more steps to run correctly.
For some situations, export/delete-original-job-and-backup-files/import might do better, for example if that would give Google Drive a
files.delete that it needs in order for the file to disappear not move to Trash. Another advantage is that one doesn’t need to worry about accidentally having two jobs with same remote (one of the adjustments one should make manually when doing an export/import to create the similar job).
EDIT: Tested 188.8.131.52 by deleting the Google Drive job. Duplicati pre-checked the database delete (then did not actually delete the database if I check with File Explorer). I had to manually check Delete Remote Files which it did do. I was watching Trash in drive.google.com, and the dlist I had seen disappeared from there.
Failure to delete the local database does not confuse Duplicati, as an import creates a new random name. Sorry I still haven’t nailed what might have gone wrong with your attempt, but at least here are some ideas.