Extract TAG ID's

Hello all, been using this tool to edit tags in my music folders. But, I'm finding I need to take a more holistic view of all my tags.
To explain, for example, I have two Aretha Franklin albums - one has a tag of "ALBUM ARTIST", the other has a tag of "ALBUMARTIST" - one or two parts of my playback methods treat these as different tags.
One thing I'd like to do is 'dump' (extract) all the tag id's in my library. Next step will be to extract/dump the actual values (data) stored.
Any advice/help gratefully received.

To see which tag fields are in your files,
load all files
select all files
Press Alt-T to open the extended tags dialogue.
There you see all the tag field names in all the files.
You may then filter for files with specific tag field names, e.g.
%album artist% PRESENT

If you want to dump the all the fields with names and contents to a text file, use an export
(see the help: http://help.mp3tag.de/options_export.html)
and have a look at the scripting function $list() (http://help.mp3tag.de/main_scripting.html)

Thank you, currently 'playing' with a subset of my library - looking promising so far.