Please can you also tell me how you got WORKSUBITLE and STYLE as that is not available in my dropdown list for defining a custom tag.
I do not wish to be rude but it is not nice to be talked down to for misreading or not understanding messages.
How to Create a Custom Tag
If you want each role separate, you must "define new tags," as presented in the first link I provided you (if you had looked at and understood @hiccup's write up, you would've understood the difference between using pre-defined tag versus defining your own),
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It is normal to use KISS when trying to explain something that is easy for you just in case the person reading the information is not used to the "terms"
More accurately, you've named a Custom Tag associated with the real tag "Involved people list" "Producer."
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It looks like from a lot of reading, experimentation, rereading the messages and rereading again - that i should define my custom tags as "save to musicbee database only"
"Save to MusicBee database only" Custom Tags are equivalent to separate Custom Tags saved to files.
You can format a "Save to MusicBee database only" tag as
role:person;, but it's not required - only the "Involved People List" tag requires this format.
Changing the producer named tag to IPLST (or another title) and define as Involved People List
Yes, then remove "Involved People List" from all the other Custom Tag definitions.
Then start the long process of editing names to role:name - where role is one of my custom tags.
That may populate my relevant custom tags "fields" with the information.
Or...
I personally would bypass the manual input (that's what really is time-consuming) and learn to use MusicBrainz Picard, as many of the albums you've tagging likely already contain the desired information in the MusicBrainz database. If not, you could add the roles to the database yourself (so others can tag their tracks appropriately) and then use Picard to grab the tags for your own files.
I believe it'll be less time consuming using Picard to add IPLS roles to all your tracks, than inputting them manually.