Use repeat, or just place seven copies of the sheet symbol on the parent sheet, either way will work. It may take a bit of trial and error to get the naming scheme how you want, but that's not too bad. Just be sure to verify that the PCB displays the correct connectivity in and out of each channel before you go too far and you'll be fine. If you use repeat, there's a specific syntax to get the individual signals in and out of the subsheet with a bus, so be sure to do it exactly as the documentation shows.
Even after the few minutes of poking it to get things right, it's still way better than manually duplicating the channels!