To avoid the possibility of it being knocked over or it being in the way, perhaps you could mount it in such a fashion as to allow it to be quickly removed and stored?
On the back of the heater there are some slots intended for mounting the heater to a wall. You could put some screws with small heads (or grind down the heads of the screws that come with the heater) into a suitable surface (I would advise a backing if you want to use a typical RV cabinet). The heater will then quickly slide onto these screws and drop down about 3/4" or so. Then, to remove the heater, just lift it up and it will come free. Turn off the valve and remove the quick disconnect and store heater and hose that is still attached to the heater in the original carton....I don't think you need two quick disconnects (more to go wrong and more $$$) A gas valve and one quick disconnect tucked away somewhere (like under a counter overhang), and a length of flexible hose to the 90 degree adapter that they sell as an accessory for the heater should do you. If you want to go a little fancy, conside mounting a gas bulkhead connector to the cabinet, with the valve and quick disconnect mounted right to it. Hose and quick disconnect can be purchased at industrial supply shops (like someplace that sells hydraulic and other fluid fittings) that will properly crimp the fitting to the hose.
Steve