Looks like you own an Anthem. Not sure the vintage (It would be a really good idea to add a signature section to all your posts so that all of us know what equipment you own when you ask a question.... minimizes the amount of bad information that you are going to get....)
Sorry ......... no remedy. You are right .... there is no heating element or process in the macerator hose compartment in my 19 Cornerstone. The macerator line is completely at the mercy of the sub zero temperatures. I think you are saying that you are doing what I would do next if in the same situation and that would be to use a 3" stinky slinky to dump rather than the macerator hose.
Now my solution to dealing with even very very cold weather like we are having right now is that I get a metal "trouble light" (the kind you use to work on a car) that has a metal shield, and put a 100W or 200W bulb in it and then I insert it under the black and gray tanks behind the panel in the wet bay. With a little ingenuity, you might be able to cut a hole that you can find a plug to fill when you dont need the hole open, and put that trouble light with a smaller bulb in it (60W or 100w) and put the light right into the macerator hose compartment and I would think that would be sufficient to keep your hose and hose connections (cam-lock)and the whole hose compartment from freezing up). Give it a try. It works great for most circumstances of giving your gray or black tanks some extra protection on really cold days/nights
Gary and Dee, Zowie and Bowie (traveling cat sibs)
2019 Cornerstone 45B, X15-605hp, Imperial, Spartan K3,
2013 Honda CR-V toad, Demco Excali-Bar II,
Demco Baseplate, Demco Toad Light system, 73 de W5FI