Here's a few suggestions:
1. Collapsible bowls, strainer, etc. can save space in the kitchen cabinets.
2. Wall mounted knife carrier.
3. Look for small modifications that can create storage such as wall mounted magazine rack for storing reading materials, tablet, laptop, etc.
4. Well labeled totes that can be transported in truck bed. Then, a tote or two with stuff that you use while camping can be slid under the trailer.
5. A lightweight box or two mounted on bumper can be used for sewer fittings, wheel chocks, etc.
6. A small ottoman can be used for a footrest in front of your sofa, and you can buy one that can be used for storage...great for an extra blanket or two.
7. Use a shoe holder that's designed to hang on bed platform.
8. Collapsable laundry hamper can be kept in shower when not using shower.
9. Mount a carrier for sewer hose.
10. If you have WD bars to store, you can make a carrier for those and mount to bumper or trailer frame.
11. With a little modification (welding the appropriate receiver), you could get a small carrier from Harbor Freight for around $50 and use it to carry gear. Remember, tt bumpers cannot support much more than the spare tire.
And, the most obvious, analyze what you really need/use while camping and get rid of stuff you don't need. Since you downsized from a larger RV, you will probably find quite a few things. We downsized from a 29' TT to a 26' trailer and are still making changes to what we carry and what we don't need.
2012 Newmar Bay Star 3302
Blue Ox Avail
BrakeBuddy Advantage
2015 Malibu
"Get busy living, or get busy dying."
Andy Dufresne, The Shawshank Redemption