These are usually found in POPUP that have fold-over cabinets etc and when you get the unit ready for travel they want to keep you from having the hot ceiling lights from being left on accidentally which might catch something on fire.
Alot of trailers especially the motorhome it seems have a kill switch located in a good spot readily available to use...
I myself have a battery disconnect switch that I installed myself to totally disconnect my batteries from the system when being stored at home etc...
If you think you have such a thing and can't find it then call the manf with your trailer VIN NUMBER and ask them...
just my thoughts
Roy Ken