why only one NotificationContainer in the app?

[Akashamba]

This should be explained in the documentation.

[dcorliss-Novetta]

It is also unclear to me whether or not it is okay to import and use NotificationsManager in several locations within the app, or if it always has to be in the same component that has the NotificationContainer. We've been seeing issues with notifications overlapping each other.

[tjrexer]

I haven't tried this use case, I also took over the project from another dev, so my answer could be completely off base.

I would expect that without a position to define, notification containers overlap which results in the behavior @dcorliss-Novetta is seeing. If you have only one notification container, then it can see what other notifications are live to not overlap.