About widget animation
When a Motion project contains a rig with a slider widget, you can use keyframes to animate the parameters modified by the slider (using the same keyframing method you use for unrigged parameters). Keyframing a slider widget lets you create powerful and complex effects where multiple parameters driven by a single widget are animated simultaneously. In rig edit mode, you can also apply Parameter behaviors to a rigged object.
Note: Pop-up menu widgets and checkbox widgets cannot be keyframed, nor can they accept behaviors.
For more information about animating with keyframes, see Keyframing overview.