Walk designer adds a key to each frame for almost every body part. You can either delete all the keys for the arm parts to stop the walk designer movements, or add a layer in replace mode and at the first frame you want the elbow bent at adjust the dial value to bend it. Just make a single bend adjustment on the one channel at a time. If you do not make an entry on the new layer then the old information remains and is active. As soon as you make an entry in a channel then that overrides the layers below the one you made the adjustment on. A very easy way to remove unwanted movement in the walk cycle. doing this you have all the movements of the walk designer except the arm elbow bent is now what you adjust on the new layer. You may want to go down the timeline and put in a couple of more adjustments to keep the cup level.

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13