The most flexible and powerful solution for Tag management for Calibre is found at
https://www.mobileread.com/forums/sho...d.php?t=247425 . It is not just a plug-in, but rather an add-on, to Calibre. Its 59 page user guide is required reading prior to installation and first use due to its functional scope and power. Usually overkill for 99.9% of users, however, but highly cost-effective for those who add a lot of books per week, and/or have large libraries that are a mess from a metadata perspective.
DaltonST