We have added the ability to remove units a tag from all units at once while still keeping the tag.
If you go to CP > Settings > Unit Tags you’ll see a new minus icon to far right of tag name in last column. If you click this it will remove that tag from any/all associated units. It will NOT delete the tag physically.
If you wanted to remove a tag physically, just remove all units, then click the trash can to completely remove the tag.
So, next time you add a ‘show tag’ to 30 units and the show is over, you can locate the tag and easily remove all units from it in one shot.