All of those buttons are actually "scenarios" which essentially are "macros" for sending commands, they aren't just menu items in the traditional sense. Of course in this case, the commands they generally send are "screen" commands that throw you into the appropriate screen for the item in question, so similar to shortcuts... Many scenarios are autogenerated based on the system's understanding of devices, which is what has happened with your other devices. However, the device that isn't appearing, simply isn't a device that it understands how to autogenerate a scenario for based on its configuration.... ie the same as most devices, because most devices don't make sense in the paradigm of a menu item.
I'm not sure about cable boxes as I haven't added one, but it seems as though one should appear for that type of device (after a full regen of course). I don't know what criteria LMCE uses to determine whether to generate one, however gut feeling would suggest ensuring that the device category is correct, Device Controlled by is set correctly, the room and entertainment areas are correct, the device controlled by category is correct, and the AV pipes are set up. These seem to be the main items that LMCE uses to determine how to treat a device....
