Frontapp is a great example on how a very simple feature makes the app very extensible!

What I mean is that I can put my own CRM custom page in the "Tabs" for Tawk.to but I need to receive some javascript event with informations about the visitor/chat going on.. this way I can add interactivity, or add per-visitor KB/links or anything I think it is useful to the agent, and I do that inside the tab "iframe" by just working with a new "agent side javascript api" (or "plugin api", like frontapp calls it) that internally works using window.postmessage.