I could have sworn I posted a reply in this thread when it was first posted, but I guess not.
I don't think there's any way for a "padding" tag to work, because each tag only knows about the values from its own track.
For example, there's no way for the tag showing "The Preacher" to know the length of the tag showing "Bye Bye Blues".
It's also non-trivial to implement because you have to account for different fonts, sizes, screen resolutions, dpi etc.
It also doesn't scale - what happens if someone shows 1000 tracks at a time?
This seems to be another case of misdiagnosing the problem and asking for the wrong solution.
If the problem is that the text isn't aligned, the best solution isn't to add padding to the text, it's to add some way to show tag values in a second (or third, or fourth...) column.
Bee excellent to each other...