Dropdown:Using Dropdowns that interact with eachother's queries

Build 824 on feat/dropdown-overhaul
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Baseline History
Build 824dddfa64
Current build. There are unaccepted changes, so build 808 is still the baseline.
Build 3234dc2de
Accepted by Adam.
Build 294a94e89
Accepted by Adam.
Build 2817e67c7
Accepted by Adam.
Commenting is disabled because there's a newer build on this branch