This is a problem that's been addressed on the forum in the past. I don't recall any "official Keystone action" being taken, but some members have added a brass elbow to their hose that connects to the city water connection and then added a "hook" or "hanger" to the side of the trailer several feet away. The elbow allows the hose to "run horizontal" for several feet, allowing it to clear the furnace vent.
There is also a 4' hose available for purchase that will allow you to move the water filter away from that location, or, it would probably be simpler to just attach the filter to the campground water faucet and then run the hose from the filter to the elbow, which would eliminate the added weight at the trailer end of the city water connection.
Here is a photo of the brass elbow that I use for my city water connection, it would allow you to route your hose horizontally and avoid the furnace vent. You can buy one on Amazon here:
https://www.amazon.com/Camco-Degree-...0062339&sr=8-1 I also believe I've seen them in WalMart's RV section and they are readily available at any RV parts store. Cost is around $5.