Well as many here I am sure after you have a trailer for a while you find theres things that really were not thought out well on the manufacturers parts or where they went cheap.
Our 2017 28.5 RSTS I couldnt stand not having the ability to dim the main living area lights. Theres 6 LED lights in the main living area and one in the hallway. During the day its fine but at night its a real PITA and way too bright.
So I bought a dimmer switch here:
You will have to open up the hole the original switch comes out of a bit. The tricky part is you take 2 wires off the original switch and the new dimmer switch has 3 wires. The new dimmer switch will have very basic instructions along with it.
The two wires on the back of the original switch were both black wires. You have to determine which one is the hot 12V wire and that will get tied to the red wire on the dimmer switch. The other black wire on the original switch goes to the LED lights and gets tied to the white wire on the dimmer switch. The third black wire on the dimmer switch goes to ground which I located behind the main control panel and it was white wires back there all tied together which meant ground to me.
I should have done a better picture layout but once I get going its hard to stop for pictures. I did take a quick video at the end to show you how it works.