https://judaism.stackexchange.com/tags and, in the "Type to find tags" search box, type in a string. The page will auto-update with tags that match that string. However, it seems based on a few tries that the string will match only:
- a real, usable tag (as opposed to a synonym), no matter where in the tag's name it matches, and
- a synonym, where it matches the start of the synonym.
(Things I've tried: searching
If this is by design, I request it be changed, and the search match even the middle of synonym names. But I suspect it's a bug.