Thanks for posting your question here!
The Plugable USB2-HUB-AG7 can be chained, although it would be preferable to plug several into one as you would have more ports and less number of tiers.
The USB standards specify that there can be a multiple USB devices connected to a single host controller via five tiers (including the internal root hub). USB devices are linked in series through hubs. There always exists one hub known as the root hub, which is built into the host controller: “USB hubs may be included in the tiers, allowing branching into a tree structure with up to five tier levels.” (http://en.wikipedia.org/wiki/USB)
The LEDs on the Plugable USB2-HUB-AG7 are indicators of the functionality (power, and devices plugged in which port, etc) and are mainly only required during troubleshooting. If the visibility of the lights are not important to you, you could stack them, although two ports are upward facing (near the LEDs) and using them might be difficult if you stack them up.
Please note that the hefty power supply provided by the Plugable USB2-HUB-AG7 is only possible when its AC wall power Adapter is plugged in and powering it up. So, do not ever forget to plug the Adapters in.
Hope the above information helps! If you need any additional information, feel free to post back here or shoot us an email at firstname.lastname@example.org. We are here to help!