Hi Jim,The Motion Key Editor works by setting transform keyframes on the timeline. When you add these keyframes CTA automatically transitions animation from one keyframe to another.
The problem you have is that when you move the characters arm CTA considers frame 1 the start of the animation and end of the animation is the keyframe when you first move the arm.
What you need to do is insert a keyframe for the arm position at the end of the idle motion. So just move the timeline to end of the idle animation and just move the arm slightly to set a keyframe. Then begin adding your arm animation keys as you did before in Motion Key Editor.