As we probably will not be keeping our trailer longer than another year I won't be investing the money (approx $400) to run an extra line. I am going with rabird's idea of an ACME type extend a flow tee.
If by that you mean "The Darkside calleth"

then you'll be able to put that hose & Extend-a-Flow T to good use since almost all hard side trailers built these days will have 1) no gas feed at all to the curb side of the trailer OR 2) a low pressure gas feed that's capped OR 3) a low pressure gas feed that terminates in a low pressure quick disconnect fitting ... I've yet to see one with a regulated high pressure feed as Fleetwood supplied on their Grand Tour series, unfortunately.

Now that you have this Extend-a-Flow you'll be able to just ignore any low pressure feed that may be on any trailer and just run directly from the tanks to your cooking location if you want to, obviously. However, I don't and the reason is simple ... our previous Santa Fe did have a regulated high pressure feed (16 p.s.i.) located on the curb side of the trailer so I'd park my Baby Q on the campsite picnic table and run the gas hose out to it from this curb side feed. I found though that having a long hose running on the ground where someone would
inevitably trip over it to be a real PITA

... and for me running one from the front of the trailer where the tanks are located would be even worse. YMMV of course but I think for now I'll just stick with using canisters or my 5 lb tank for running my Baby Q and stand alone Coleman two burner camp stove but it sure would be handy if trailer manufacturers would all adopt Fleetwood's idea of supplying a regulated high pressure gas feed on the curb side of their trailers that could universally be used for powering a variety of propane powered appliances.