I don't know about your particular tractor, but you may not want to do that. (You may also be at max extension). I have a JD ~50HP and if I'm on a slope the outrigger can lift the downhill side of the tractor a little, but then the stability of the tractor/backhoe is reduced. The outriggers are not enough to stop the tractor from sliding while I'm digging, I need the tires in contact with the ground and the outriggers for tipping control and to help make the boom vertical so the trench is not undercut. I try to keep both tires on the ground and brakes set with just enough outrigger down pressure to stabilize the tractor and tilt it for a vertical trench - and put the bucket on the ground also.
But to answer your question directly, yes, the outriggers should be able to lift the tractor a little. Your cylinders may be to short or your pressure may not be set correctly.
Note: Construction backhoes are capable of lifting the entire backend of the hoe with just down pressure on the boom and move the tractor around that way which makes crossing trenches possible. Farm tractors with a backhoe can not do that.