Thank you! I understand now. :)

Sent you the files. Aside from me being on Mac, another difference between my example and the Card_Arrow flame spinner is that's a mesh, and I'm using a Sprite. When I change it to a Mesh, it spins properly in play mode.

Ok, will do.

Possibly related, I'm seeing a NullReferenceException somewhere along the way.

NullReferenceException: Object reference not set to an instance of an object
UnityEngine.GUILayoutUtility.BeginLayoutGroup (UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options, System.Type layoutType) (at /Users/builduser/buildslave/unity/build/Runtime/IMGUI/Managed/GUILayoutUtility.cs:296)
UnityEngine.GUILayout.BeginHorizontal (UnityEngine.GUIContent content, UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options) (at /Users/builduser/buildslave/unity/build/Runtime/IMGUI/Managed/GUILayout.cs:306)
UnityEngine.GUILayout.BeginHorizontal (UnityEngine.GUILayoutOption[] options) (at /Users/builduser/buildslave/unity/build/Runtime/IMGUI/Managed/GUILayout.cs:293)
ShaderWeaver.SWWindowLayoutV.OnGUI () (at Assets/ShaderWeaver/Plugin/Scripts/Editor/Window/SWWindowLayoutV.cs:268)
ShaderWeaver.SWWindowMain.OnGUI () (at Assets/ShaderWeaver/Plugin/Scripts/Editor/Window/SWWindowMain.cs:283)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture