Use the single groove toolpath in Fusion

Before the tool has been selected for an operation, right-click the tool in the Fusion 360 Sample Library and select Edit Tool

Export the tool geometry as a .f3d file and edit it in the Design Workspace

There is no way to modify the geometry of tools from the Fusion 360 Library

After a tool has been selected for an operation, right-click the toolpath in the Browser and select Edit Tool