https://phabricator.wikimedia.org/maniphest/query/advanced/ shows, by default, fields like "Reference" which are uncomprehensible.
To be as user-friendly as bugzilla's advanced search, less used fields should be collapsed by default and enabled by the users who need them.
"Reference" is our custom field to find tasks migrated from fab, Bugzilla, RT...
As for the rest... It's an advanced search. I think "obscure fields" is an exaggeration. Proposing Declined.
That field could be named better (and since it's custom I imagine it's not a complex change).
We now also have the rather obscure "Query (prototype)" which apparently refers to the new fulltext engine but that's from upstream and presumably temporary.