Unless the WD bar end is jammed against the side of the cam, I see no reason why you can't,after you have released the chains, just push down on the cam/arm surface to release the tension. Those arms should be able to be pushed down all the way to the ground or until they are nearly vertical.
If your WD bars are jammed against the side of the cam or arms, then you need to take a look at your installation to make sure it is ok. This is if your truck and trailer are lined up straight. If they are not, or if your truck is pitched one way and the trailer the other, then the bars could possibly jam somewhat against the cam. In that case you would need to push very hard down on the cam arm or the cam surface or even the WD bar end. I can remember at least one time when I had to stand on the bar itself and jump up and down to push the cam down far enough to remove the bar.
Barney