I think this may be a reasonable case for the (re-)introduction of an additional smaller field than the current 'Small' width.
With the latest versions brings the ability to change the field size of any tag field so the widths were normalized as everything is now customizable, however prior to this the Year and Track occupied half the current equivalent width of a 'Medium' (half) width field each:
Example mock-up beside current 'Medium' width fields:
Adding such an additional smaller field width would help for smaller value tags while still allowing people to keep 1/3 width fields as we do currently with the 'Small' width field (which is useful for those who store longer values for Year, etc).
Only thing one would have to keep in mind should a smaller width be implemented (for custom tag fields) would be the potential for field labels longer than like 8 characters to truncate, potentially making some labels illegible at smaller Tag Panel widths. Not a huge issue though, the user could easily adapt if they needed use of a smaller field.