My intent was to create a few tags then later assign them to scenes. After creating a five tags is when I made the backup. It appears that the tags are not saved if they are not assigned to a scene. For example, I added a tag to Farger's nebula spheres called "space". The tag "space" appears in the tag dropdown and I am able to back it up. However, if I uncheck the box to remove it from nebula spheres and do a backup the tag will disappear. I did not receive an error message and I am using version 58. For now my workaround will be to simply assign all new tags to one scene and leave them all active during backups.