Showing all valid options is not feasible (Tried it, ran out of memory trying to aggregate them all [grumble, grumble, app engine])
I can update the mouseover that (incorrectly) says "these are all of the options that can be filtered on"
I feel like it would be better to have some type of indicator in the actual list rather than just the info in the tool tip.
Maybe just a "..." item which always appears after all other items?
Comment 1 by kjlubick@google.com
, Nov 15 2016