Hi, and thanks for the followup.
Yes, I think the reason for these various posts is what I was pointing out: That people are now using more custom tags and they want a flexible way to keep track of all the ways they're using those fields.
Here's the problem: mp3tag assumes the user will be fine with just seeing whatever tag values come up contextually when viewing a certain group of files. But what if I've got 30 or so values that I want to choose from, but which don't exist in the particular files I've selected? Now I have to either manually remember the values, or do workarounds (sample files, actions, etc.) But when other utilities and players dynamically provide dropdowns with all values (in a library, for example), this just seems tedious and makes mp3tag laborious to work with.
That's why a configurable dropdown list is optimal for this situation. Why not make it optional and user-configurable? Typical users wouldn't use the feature, but for users like me and the other recent posters, we could set it up and use it.