To view multiple skins at the same time in the Spine editor, you can use the Skins view. This feature allows you to pin multiple skins so they are visible simultaneously in the viewport. To do this, open the Skins view and pin the skins you want to see together. This will help you ensure that all parts, like shoes, legs, and eyes, are displayed correctly when working with multiple skins. Unfortunately, there isn't a direct way to apply a "Default" skin that combines all skins, but using the Skins view to pin multiple skins is the best approach to achieve a similar result.
For more information, you can refer to the Skins view - Spine User Guide.
