It's very hard to follow what you've done. I can't really follow it. You are talking about auto import files and non-auto import files. You're also saying auto import doesn't work. Most of the time, auto import doesn't work because of a NAS system that doesn't support file system events. Where are you files? NAS, local, external USB?
I've never wrote about that (but the music is on an external USB3 harddisc permanently connected).
I made screen shots to describe what I did what others have recommended. Thought it would be helpful.
But let's back up a step. You just want to update a few files (around 100 of them) that have modification times in the past few days right?
This was my initial request.
Easy. Just go to a view in MC that shows all files, and add a column to the view: Date Modified. Now sort by Date Modified. All of the most recently modified files will be at the top. Select the ones you want and run Library Tools > Update Library (from tags) . Done.
I just tried it but it doesn't work.
Test:
1. I have imported 20 files into MC and added column "Date Modified" and exit MC.
2. I start Serato, import the same files/directory, update a title of a track and exit Serato. Serato has saved the tags back to the file and "Date Modified" has changed of course.
3. I started MC and still see the same files + content after step 1 - without any change of title or "Date Modified".
Finally sort by "Date Modified" does not bring the changed file up because of the old Date Modified content is in the library. So I can not select and update tags from the latest updated files.
---
What works is when I select "Tools / Import / Run Auto-Import Now" which then updates the library from the files and inserts the files.
I've to test later if MC reads tags of all 60.000 files although the Date Modified timestamp didn't change (only a few did change). Only re-reading tags of changed Date Modified timestamp files would be required.
Thanks!