End goal:
Use Tag-Tag converter to copy existing lyrics from the “TXXX” frame to the “USLT” frame.
Intermediate goal:
Create two custom columns; one that shows lyrics already in the USLT frame, and one that shows them in the TXXX frame. This will allow me to easily determine which files need correction. I am not 100% sure this goal is strictly necessary. However, I’m pretty sure I need to confirm the exact frame I’m copying from, and I’m having a hard time identifying it in Mp3Tag.
Starting point:
I used Foobar2000’s OpenLyrics plugin to bulk download lyrics and changed a setting I should not have. This appears to have caused the lyrics to download to the TXXX frame instead of the USLT frame. My Android music player, Musicolet, requires them in the USLT frame. I (believe I) have corrected the setting in Foobar so this should not be an issue going forward.
That said, I have quite a few files that I need to correct, and if I have not actually corrected the root problem, I may need to correct more in the future.
What I’ve done:
Read the Mapping documentation - I can’t see how it would apply to my issue (not saying it doesn’t, just that I can’t figure it out) 
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Read several threads that appear to be related but don’t seem to have applicable information
Tried several permutations of custom column names; example below.
MP3 Diag shows “Gin and Juice“ as having the lyrics in the USLT frame:
MP3 Diag shows “The Transformers theme” as having the lyrics in the TXXX frame:
However both songs show the lyrics in column that I have tried to assign to the “unsyncedlyrics” frame (column title “USLT Lyrics (I think)”):
And do not show lyrics in the column I have tried to assign to the “TXXX” frame (column title “TXXX Lyrics”)
