To update Spine assets in Unity without creating duplicate names, you should avoid dragging and dropping the assets directly into the Unity editor. Instead, follow these steps:

1. Export the updated assets from the Spine Editor: Ensure you have the latest .json, .skel.bytes, .atlas.txt, and .png files.

2. Replace the files via file explorer: Use your operating system's file explorer or command line to copy the updated files directly into the appropriate folder in your Unity project's Assets directory. This will overwrite the existing files without creating duplicates.

3. Reimport the assets in Unity: If Unity does not automatically detect the changes, you can manually reimport the assets. In Unity's Project panel, right-click on the folder containing your Spine assets and select Reimport.

By following these steps, Unity should update the assets while keeping all references intact, avoiding the need to re-script or reassign animation nodes.

For more detailed instructions, you can refer to the spine-unity Assets documentation.