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TheMadGuy - some of what you want can be achieved with custom columns e.g. here's my custom column definition for Subtitle
The Author and Title column names are 'nominal names', in my Journals library I use them for Journal Name and Issue Identifier respectively - e.g London Review of Books and Volume 38 Number 19.
I tag via Shift+F2 in the Book List, which pops up the Tags Editor dialogue, it's a more deliberative user interface, so there's less chance of creating spurious entries or assigning the wrong ones.
BR