Using the official web version?
Open the page
https ://www.beeminder. com/tags
(slug tags is a special slug like payment, breaks, reminders, and some others and is not a username)
A search of help.beeminder.com for the word tags brought up nine results, none of which appeared to be relevant.
Using the official API?
One update a goal by setting its list of tags.
https ://api.beeminder. com/#attributes-2
Using the official iOS app?
Not at all (currently)
Unofficial client?
Try altbee
Altbee — the alternative Beeminder web interface / https ://altbee.aeonc. com/ / https://github. com/quantified-self-tools/altbee/
There they are discoverable and work as you would expect.