It would be great to have a way to create custom commands or manipulators to batch tags edits, similar to the swap functions currently under the edit menu. The current functionality of the “Rename File From Metadata” masks builder is great and extending that capability to tagging could be really powerful.
An example usage, (but not limited to) would be classical music tagging. Classical music metadata seems to be really inconsistent when it comes to online lookups.
The ability to create a manipulator or routine that says “if empty, Sort Album Artist = composer + orchestra + conductor” would really help fixing a large library.