I couldn’t find a post about this, although I remember there is a conversation somewhere where this is talked about. It would be awesome if there is a display, like there is for links and tags, that shows the documents or rems that contain a portal to any rem.
Currently this seems to be displayed in the “In X document(s)” box inside a rem, but that is very subpar to the alternative, display it the same way the links and tags are displayed.