Our plan has been to have all Search&Discovery issues managed in the Search-Team phabricator project, and then for each subteam to have a sprint board for its current work.
However, Yuri pointed out that people wanting to create a new task related to maps would expect to add it to a project with "maps" in the name. Folks outside our team often would not realize that maps are part of the Search vertical.
We really want to consolidate all of our product backlogs in one place, to help keep Dan sane. So I don't think keeping an external high-level "Maps" project is a viable option. And I don't think adding the word "maps" to the main Search-Team project would make sense either. We might want to rename our top-level project to "Search-and-Discovery-Team" for other reasons, but that wouldn't help this specific case.
Even if we had a maps-related sprint board whose name would match a phab search for "map", that wouldn't be what we would want. We don't want random users dropping tasks directly into our sprint board. We really want new tasks to land in the product backlog first.