Saw that the dev that wrote tag wrangler has no intention on adding a Delete tag function:
“(I’ve considered adding tag deletion as well, but given that it’s a destructive operation with no undo, well… seems better to do it with an interactive search and replace, or to just merge the tag into another tag – i.e. rename it to the same as an existing tag. This will “delete” the old name from the tag pane, at any rate.)”