How do I clean ununsed tags from Finder? I seem to have accumulated a number of tags, some of which are duplicate and which do not belong to any files. I can see these tags when I open All Tags. These I assume were set for some files, which were then deleted.

How do I clean up the Finder so that only the current tags are present?
Open Finder preferences either by going to Finder → Preferences in Menu bar or by pressing Command + , keyboard shortcut with with Finder.app open.

Go to Tags tab, select the unwanted tags and hit - button.