Easiest way would be to just run the cable from the rear wall plate to the tv in the slide. This would require enough slack to run the slide in/out. If you don't plan on ever using that wall plate again, you could disconnect it and pull the cable down from the wall by removing the coroplast enough to reach it and thread the cable thru the frame near the electrical box under the slide. Follow those electrical cables to the outside rear corner of the slide where those wires go up into the slide to the electrical box on the rear of the slide. Add your cable wall plate that you removed from the rear next to that outlet box and fish your cabling to that. You should have to coax cables to move, one for OTA and one for cable/ satellite.
Make sure you turn off the power to the trailer before you work around the electrical outlet in the slide.