Designate tags in Filter which do *not* appear in the Filter controls
As it stands, all tags that are assigned to a filter item are automatically displayed by the Filter stack in the Filter controls stack (when set to display tags).
However, I would the option to tag the filter items with tags that can be used to filter the items, but which *do not display* in the Filter controls.
One use case: I am intending to list my scientific publications. I would like to tag these by topic area, and would like the user to be able to filter by these tags. However, I'd also like to tag a publication by additional information (such a code that represents to the scientific talk in which I spoke about that publication). The latter kind of tag is not something I want the user to see (within the Filter), but would still be useful as I can call the filter (from elsewhere on my site) with a code that refers to a particular scientific talk (for example) and have the list of relevant publications be automatically displayed.
As for UI implementation: there could be *two* lists of tags—one list contains tags that ARE displayed in the Filter controls; the other contains tags that are NOT displayed.
Alternatively, one could just allow prefixing of a tag by % to indicate that it should not appear in the Filter controls.