To preview custom skins inside the Spine Editor without being in play mode, you can utilize the skeletonRenderer.EditorSkipSkinSync property. This property, when set to true, prevents the SkeletonRenderer Inspector from calling the code parts in UpdateIfSkinMismatch, allowing you to maintain your custom skin setup in the editor. This method is described in the context of dynamic attachments showing in the editor and is a recommended approach for managing skins within the editor environment. For more detailed information, you can refer to the discussion on Dynamic Attachments Showing in Editor.
Regarding the preview of animations in the editor, the current Spine-Unity setup does not provide a built-in feature to preview animations frame by frame in the Unity Editor outside of play mode. The typical workflow involves entering play mode to see animations and transitions as they will appear. However, you can adjust the inspector window size to make the preview window larger for a better view of the animations, or you can create and use animations as a library to activate and deactivate assets at once for easier management.
