Synapse is a tool in the Motion Dock that draws lines between layers and keeps them attached while the layers move. You don’t keyframe the lines or rig them with expressions yourself. Select the layers, click a tile, and the lines follow every move, parent and camera.
The top of the panel is a small night sky. With nothing selected it shows a ghost constellation and Select two or more layers.
Below it are the three tiles, Chain, Hub and Web. Each one links your selected layers a different way.
The sky shows your layers
Select two or more layers and each one appears as a star, placed where it sits in the comp. Select a Synapse and its lines appear between the stars.
The caption at the top counts what you selected, or the lines in the selected Synapse.
Three ways to link
Hover a tile and the sky previews the lines it would draw.
Chain links the layers one after another in the order you selected them. Hub links the first layer you selected to every other one. Web links every pair closer than a distance you set and fades each line out as its pair drifts apart.
Choose Chain, Hub or Web compares them.
One layer holds the lines
Each click makes a shape layer named Synapse with all of its lines and one effect, also named Synapse. The effect sets the lines’ width, color, sag, distance and how much of each line is drawn. Animate it like any effect. The Synapse layer and effect lists every control.