Is it possible to set a criteria in Herald that says "look for X project, and all Milestones thereof"?
For instance, a team wants to have weekly Milestones on their backlog, and they use a separate board for their Kanban. In a process in which all Kanban tasks need to be reflected on the backlog (in case, say, someone added a brand new task to the Kanban, but skipped the backlog triage process) for one-source-of-truth, Herald can look for those stragglers. Example: https://phabricator.wikimedia.org/H269
With Milestones, I'm under the impression that Phabricator treats each as its own project, so Herald has to be updated for each Milestone.
Updating Herald for weekly Milestones isn't hard, but it's a little tedious, and it adds weakness to the process (e.g. the changes have to be requested; or, each change to the Herald is a risk in and of itself should a mistake occur). It would be useful to be able to tell Herald to look for subprojects of a project, to automate this.