I don't know of a way to do this (Andrew may know of a way), but you can view the tags list and see all the tags without numbers next to them. But if you want to include completed tasks, you'd have to go into each tag and check.

I'd like to 'archive' those tags. That is, I would still like to have them attached to completed tasks, but just not see them anymore.

@blackshift - Having the ability to archive tags is a great idea. You should add that to the Ideas forum for people to vote on. I'd vote for that feature.

I do this on several platforms:

Create a tag called “Z-old”. Change the empty tag name to “Z- and make it a sub tag to Z-old.

This keeps them on all tasks - accounting for possible completed tasks. This allows me to roll them up to 1 task name at the very bottom of my tag list - out of sight.

It's not possible to delete empty tags automatically, but you can hide them in the left navigation bar.

Archiving is available for lists, but not for tags. It may not be appropriate in all circumstances but you can create a list, move the tasks to that list, and then archive that list to keep those tasks organized.

(That just falls apart if you use a lot of tags across tasks, since tasks can only be in one list.)

Thanks for all the feedback though! Yes, voting in the Ideas forum would be welcome if you want to see any of these or add your own ideas about tags.

I did not follow your last few paragraphs Andrew.

It would be nice for a way (perhaps in the settings) to just "Remove all unused tags" (specifically tags with no complete/incomplete tasks with them).

Also, thank you geojono, blackshift, and azclaire, for responding to my query.