Hi Paul Gormley, nice to meet you.
Although I am breaking the barrier of 2.000 forum postings these days, I am not the maker of the Mp3tag tagging application. It seems so, that you are not so much informed about this magic software called Mp3tag founded by Florian Heidenreich.
There are several locations to read about the Mp3tag Filter feature.
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Mp3tag Manual.
Online: https://docs.mp3tag.de/filter
Offline: See Mp3tag Main Menu / Help or press context sensitive key [F1].
The german help file contains a few more Filter examples than the english online version. -
Mp3tag Forum.
Mp3tag Forums > Mp3tag - International > Support
Important Topics > Pinned: Filter expressions
/t/10080/1 -
Mp3tag Forum.
Questions and answers from Forum users.
Regarding your other questions ... there should come in other Mp3tag users, who have much more experience in these practical areas than me.
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