I'm using ArcGIS API v4 and the document said ArcGIS API allows view can only have one instance of popup at a time
All Views contain a default popup. This popup can display generic content, which is set in its title and content properties. When content is set directly on the Popup instance it is not tied to a specific feature or layer.
I've been searching for similar questions but still got no clearly answers? Is there a way to implement opening multiple popup on ArcGIS map at the same time?