Another alternative to a ladder is is a wider seat step. Ours is twice as deep as this pic I stole from a for sale ad. Much more stable than a ladder. I use one of those small fold up steps in addition to this, so very very stable for getting in and out of bed.
It has two legs which go through small holes in the canvas and into slots under the trailer, so not going to move on you once installed. Very flat for storage.
So that's what i have at the moment, and yes its quite sturdy and doesn't wobble but i am finding the step is only about 300-400mm off ground level, and then its a big swing to get up and onto the far side of the mattress, over the sleeping partner, in the dark, without waking the dog, after a few beers.
I thought a ladder might make things a bit easier.
So if the ladders are perhaps a bit less stable than steps, then I wonder if attaching a disabled handrail like this to the bed floor near the mattress would make it easier: