Ref T12956. Currently, when you visit /maniphest/ (or any other ApplicationSearch application) we execute the first query in the list by default.
In T12956, I plan to make changes so that personal queries are always first, then global/builtin queries. Without changing the "default query" rule, this will make it harder to have, for example, some custom queries in Differential but still run a global query like "Active" by default. To make this work, you'd have to save a personal copy of the "Active" query, then put it at the top.
This feels a bit cumbersome and this rule is kind of implicit and a little weird anyway. To make this work a little better as we make changes here, add an explicit pinning action, like the one we have in Project ProfileMenus.
You can now explicitly choose a query to make default.