Carry stuff you use outside in the truck and stuff you use inside in the trailer.
For me in the truck are folding chairs, table, tub filled with leveling blocks, extra hoses, cables, BBQ and 5lb propane tank, portable solar panel, future small generator, patio mat, tools, ice chest. I have a pull out rear bumper tray so all my hoses, extension cord, water hook items go in there along with a sewer extension hose.
Inside, clothes, bedding, food, cooking utensils. Still have under the bed available for extra clothes for extended trips.
You may want to get a tonneau cover or shell for your truck.
There is probably more storage in your 23fb than my 25fb.