You an get alternate ends for the Rino.. you need a male end, and as noted a short length of hose (Just cut it off) and a female end.
then do as the photo.
My rig is a bath and a half, The shower and rear (full) bath has it's own "Wash" tank (Technically it's wash, not gray) I use a 25 foot Gray 3/4 Inch Garden hose and on some of my hose ends (the elbow at the ground) there is a male hose fitting. by use of an adapter cap on the RV, I put the shower in that fitting,,, Works well... Very well. But your elbow does not have that fitting.
What is the difference between Wash and Gray... The Kitchen Sink (Food particles).