As I have many mixed albums (fx. Best of 2010), I usually choose to hide the songs which I'm not going to transfer to my mp3 player, but which I want to keep for archival purposes. If it therefore was possible to check an option named "Do not show hidden files" inside mp3tag I would be very pleased. The list of files in each album would certainly decrease in amount of songs to tag (which I do by hand).
I did a search on the forum, but couldn't find any similar suggestion in the first place. However, I'm sorry to waste your time, if this has been suggested before.