I administrate our Phabricator instance for our business.
One of my coworkers had some complaints regarding the default queries for tasks, and wanted to change them. We reasoned out that he could save a custom query for the information he wanted, although we both agreed that there would be some value in the ability to easily share that query (and perhaps others), with other people in the company, without everyone having to make their own version.
I think this is currently possible through the use of Dashboards, but that requires viewing from outside Maniphest (or any relevant application).
Some searching also suggests that the current go to is to share a link to the query.
I'd personally appreciate a way to specify default queries on a per-application basis, but I realize that may be out of scope, and/or not really necessary given the existing options.