How is working the hidden interface bridge100?

This interface bridge100 have been introduced with Mavericks and exists on Yosemite. (On Mountain Lion the same kind of mechanism was taking place with the bridge0).

This interface is related to the starting of Internet Sharing. When Internet Sharing is off:

$ ifconfig bridge100
ifconfig: interface bridge100 does not exist
$

When Internet Sharing is on:

$ ifconfig bridge 100
bridge100: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICASRT> mtu1500
        options=3<RXCSUM,TXCSUM>
        ether ••My_Ethernet_@MAC••
[...]

But this interface doesn't appear within System Preferences > Network.

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Where is the correct documentation about this hidden interface?

How to make this interface appear within the System Preferences > Network list of interfaces?

How is this interface configuration managed?