How to draw a circular path in flash fill-in animation

First, first create a guiding layer, then create a new layer, in this layer create a component (note that only components can do path animation)

Second, click on the adsorption tool, adsorption of the component's registration point (the small white dot in the center) to the path

Third, to create the fill-in-the-blanks, if you want to make it go around in a full circle, you want to insert a few more keyframes in the middle. The last frame duplicates the first.