Wave hand/arm

Triggers by default make a hidden layer visible. If the hidden layer contains a series of frames with A Cycle Layers behavior added, you can cycle through fixed hand positions you draw in the artwork file (the display frame by frame). It works. You can use forward/reverse with hold-on-last-layer nicely. That is one approach. But the keyboard trigger just causes other images to be displayed.

The alternative is to use a dragger and a replay. You can add a dragger to the wrist then make a recording using your mouse to wave the hand. You can just use that recording directly in your scene. But if you want to hook it up to a trigger, then you select the region of the recording you made and can then convert that subset into a “replay”. You can then add a keyboard trigger to play the replay. It effectively plays back the recording each time you press the key.