Hi,
It is under tools -> Options-> Library -> Fields

So these instructions no longer apply in MM5 as there is no "Appearances" under Option.

What do I do?

Duh.

Don't know how I missed that. Underestimating the thoughtfulness of the programmers again...

Big thanks.

Are you talking about something other than,
Options > Appearance > change names of custom fields at bottom of dialog?

It would be awesome if I could customize the File Properties dialogue box and column names for the ID3 tags "Custom 1", "Custom 2", "Custom 3"...

I use these heavily to augment the kind of database searches I do every day as part of producing a weekly radio show. I am extremely grateful you included them as nothing like this appears to exist in other programs. But if I could change the names, it would frost my cake.