Stabilizers. There are a couple different types and several mounting methods. Some can bear weight, others can't.
The kind that fold down out of a bumper or are stored horizontal and drop down like landing pads, these are only for stabilizing not bearing much weight and could collapse if asked to do so.
Scissor jacks that drop straight down, like the OP has, are actual jacks and designed to bear weight. BAL ( the most common manufacture for the ones on RVs) rates the jacks at 5000lbs each. What is important is where and how these jacks are mounted. If they are attached on a small cross member or outrigger the structure will not support much weight, attached to a primary frame member they can.
From the picture, the OP has scissor jacks mounted to spacer tubes attached directly to the main longitudinal frame members. These jacks absolutely can support the weight of the trailer mounted this way, and the front ones be used together to take weight off the tongue jack.
I have BAL scissor jacks mounted in a similar fashion, I have on more than one occasion used the front jacks to support the front of the trailer while doing something with the tongue jack.