Bigger tires if there’s room will help, minimally. Probably can’t go more than an inch taller ? So gain 1/2”.
Stouter springs or spring over axle lift is possible but has its downsides.
Temporarily lowering the hitch height at the truck as low as possible will help the most for the least amount of effort. IMO. Only requires unhooking the trailer to level it up for towing.
Goofy idea, if you could rig up air shocks or airbags on the rear trailer axle to give it temporary lift with just air, that would be slick.
Last suggestion, depending on layout of jacks etc, is adding some casters to the bottom of the frame rails at the rear , assuming the trailer just needs a little help and you won’t be actually supporting near the whole trailer by the casters.
Hope this helps
All I can think of besides tossing boards.