I can't tell you if Keystone installed a sewer hose storage kit on that model or not, but there are several "aftermarket solutions" that usually provide better options than the "low bid factory equipment"...
If you do a "forum search" for the term "Sewer hose storage" you'll get more than 160 threads that discuss that topic.
Here are some threads that might help you:
https://www.keystoneforums.com/forum...r+hose+storage
https://www.keystoneforums.com/forum...r+hose+storage
https://www.keystoneforums.com/forum...r+hose+storage
https://www.keystoneforums.com/forum...r+hose+storage
https://www.keystoneforums.com/forum...r+hose+storage